Download Chapter 1 questions

Extra Chemistry questions from Ellett book.
Chapter 1 questions
1. Definition of important terms
Q1.
Define the following terms:
a) element
c) mass number
e) ion
f) relative molecular mass
h) molar mass
i) molecular formula
b) atomic number
d) isotope
f) relative atomic mass
g) mole
h) empirical formula
j) Avogadro constant
2. Calculation of Relative Atomic Mass
Q2.
The element lithium has two isotopes, 6Li and 7Li. The relative isotopic mass of
6
Li is 6.02 and of 7Li is 7.02. Their percentage abundances are 7.4% and 92.6%
respectively. Calculate the relative atomic mass of lithium.
Q3.
Calculate the relative atomic mass of each of the following elements from the data
provided in the table below:
Element
a) Sulphur
b) Silver
c) Magnesium
d) Silicon
Relative Abundance (%)
Relative Isotopic mass
95.1
0.70
4.2
48.18
51.82
78.8
10.2
11.0
92.2
4.7
3.1
31.97
32.97
33.97
106.91
108.91
23.99
24.99
25.99
27.98
28.98
29.98
Q4.
The relative atomic mass of chlorine is 35.45. The two natural isotopes have
isotopic masses of 34.97 and 36.98 respectively. Calculate the percentage abundance of
each isotope.
Q5.
The relative atomic mass of gallium is 69.72. The two natural isotopes have
isotopic masses of 68.95 and 70.95 respectively. Calculate the percentage abundance of
each isotope.
1
3. Empirical and Molecular formulae
Q6.
Calculate the percentage composition of the following compounds:
a) HCl
b) NaCl
c) H2O
d) CuSO4
e) Mg(NO3)2
f) H2SO4
Q7.
An oxide of sulfur contains 40.0% by mass of sulfur. Calculate the empirical
formula of the oxide.
Q8.
Analysis by mass has indicated the following percentage composition by mass of
certain compounds. Calculate the empirical formula of each:
a) carbon 75.0%, hydrogen 25.0%
b) magnesium 60.3%, oxygen 39.7%
c) iron 69.9%, oxygen 30.1%
d) potassium 24.7%, manganese 34.8%, oxygen 40.5%
e) tin 52.8%, iron 12.4%, carbon 16.0%, nitrogen 18.8%
Q9.
Nicotine is a highly toxic chemical which is strongly addictive when ingested,
generally through the inhalation of burning tobacco. The relative molecular mass of
nicotine is approximately 160. Quantitative analysis of this compound yields the
following percentages by mass of its constituent elements:
carbon 74.1%, hydrogen 8.7%, nitrogen 17.2%
Calculate the empirical and molecular formulae of nicotine.
Q10. 0.8361g of an organic compound is analysed and found to contain 0.4565g of
carbon and 0.0761g of hydrogen, with the rest of the mass being made up by oxygen. The
molar mass of the compound is 88 g.mol-1. What is the molecular formula of the
compound?
Q11. One method which can be employed to qualitatively measure the amount of
alcohol in the breath relies on the colour change from orange to olive green which results
from the reduction of a chromium salt by the alcohol. A more accurate determination can
then be performed by a blood test. If the percentage composition of this chromium salt is
as follows, determine its empirical formula:
potassium 26.58%, chromium 35.35%, oxygen 38.07%
Q12. A naturally occurring compound is known to contain the elements carbon,
hydrogen, nitrogen and oxygen. To determine its empirical formula 6.25g of the
compound was completely burnt in oxygen to produce 3.75g of liquid water and 5.104 L
of a gaseous mixture containing only nitrogen and carbon dioxide. This gaseous mixture
was then bubbled through a concentrated solution of sodium hydroxide to extract the
carbon dioxide. 1.021 L of nitrogen gas was left unreacted. All gas volumes are given at
standard laboratory conditions (S.L.C.)
2
(i) Using the mass of water produced, calculate the mass of hydrogen present in
the compound.
(ii) Using the volume of carbon dioxide produced, calculate the mass of carbon
present in the compound.
(iii) Using the volume of nitrogen gas produced, calculate the mass of nitrogen
present in the compound.
(iv) Hence, deduce the mass of oxygen present in the compound.
(v) Determine the empirical formula of the compound.
4. The mole and Avogadro constant
Q13. Calculate the number of moles present in
(a) 36.0g of water
(b) 51.0g of ammonia
(c) 500 kg of iron (III) oxide
(d) 25.0 ml of 0.60M HNO3
(e) 4.8L of 1.25M NaOH
(f) 1.2 x 1022 molecules of methane
Q14. Calculate the mass of
(a) 6.38 mol of UF6
(b) 0.049 mol of Na2S2O3
(c) 1.65 mol of acetylene (ethyne)
(d) Al2(SO4)3 in 10 L of 0.035M solution
(e) 1.0 x 10-6 mol of gold
(f) 8.875 x 1025 molecules of KMnO4
(g) one molecule of water
Q15. In 28g of sulfur dioxide, calculate
(a) the number of mol of SO2
(b) the actual number of molecules of SO2
(c) the number of atoms of sulfur present
(d) the total number of atoms present
Q16. The female members of many species of moth secrete particular chemicals known
collectively as pheromones to which the male of the species is strongly attracted. One
such material has the molecular formula C11H18O2, and it is reported that the male will
respond to as few as 60 molecules of this material. To what mass (in grams) does this
correspond?
3
Solutions to Chapter 1 questions
Q2. 6.95
Q3. a) 32.06, b) 107.95 c) 24.31 d) 28.09 Q4. 76.12%, 23.88%
Q5. 61.5%, 38.5%
Q6. a) H = 2.74%, Cl = 97.26% b) Na = 39.35%, Cl = 60.65%
c) H = 11.11%, O = 88.89%
d) Cu = 39.81%, S = 20.09%, O =40.10%
e) Mg = 16.39%, N = 18.88%, O = 64.73% f) H = 2.04%, S = 32.69%, O = 65.27%
Q7. SO3
Q8. a) CH4, b) MgO, c) Fe2O3, d) KMnO4, e) Sn2FeC6N6
Q9. C5H7N, C10H14N2 Q10. C4H8O2
b) 2.00g, c) 1.1669g,
Q11. K2Cr2O7
Q12. a) 0.4167g
d) 2.666g, e) C2H5NO2 Q13. a) 2.0 mol, b) 3.0 mol
c) 3,310 mol d) 0.015 mol, e) 6.0 mol, f) 0.0199 mol Q14. a) 2246 g, b) 7.748g
c) 42.9 g, d) 119.7 g, e) 1.97 x 10-4 g, f) 23.3 kg g) 2.99 x 10-23 g Q15. a) 0.437 mol
b) 2.63 x 1023 molecules, c) 2.63 x 1023 atoms, d) 7.89 x 1023 atoms Q16. 1.81 x 10-20 g
Chapter 2 - Questions
1. Chemical and Ionic Equations
Q1.
Write balanced equations, including states, for the following processes:
(a) When an electric current is passed through water it decomposes to its constituent
elements.
(b) A dilute solution of hydrochloric acid dissolves a strip of magnesium to produce a
solution of magnesium chloride and hydrogen gas.
(c) Sulfuric acid reacts with a solution of potassium hydroxide to produce potassium
sulfate and water.
(d) Propane undergoes complete combustion in excess oxygen to produce carbon dioxide
and water.
(e) Aluminium metal reacts slowly with hydrochloric acid to produce a solution of
aluminium chloride and hydrogen gas.
(f) Marble chips (calcium carbonate) dissolves in a solution of acetic acid to produce a
solution of calcium acetate, carbon dioxide gas and water.
(g) When solutions of potassium iodide and lead (II) nitrate are mixed, a bright yellow
precipitate of lead (II) iodide is formed.
(h) On standing, hydrogen peroxide spontaneously decomposes to water and oxygen gas.
4
(i) When carbon dioxide is bubbled through a solution of limewater (calcium hydroxide)
a milky precipitate of calcium carbonate is formed.
(j) Solutions of silver nitrate and sodium chloride are mixed to produce a white
precipitate of silver chloride.
Q2. Use your knowledge of general reaction types to write balanced chemical equations
for each of the following reactions:
(a) solutions of nitric acid and sodium carbonate are mixed.
(b) sodium metal is added to water.
(c) butene is burnt in a plentiful supply of air.
(d) solutions of strontium iodide and lithium sulphate are mixed.
(e) zinc metal is placed in a solution of copper sulphate.
(f) aluminium sulphide reacts with hydrochloric acid.
(g) calcium carbonate decomposes to calcium oxide upon strong heating.
(h) sulfur dioxide gas is bubbled through a solution of potassium hydroxide
(i) incomplete combustion of methane in a limited supply of air results in the formation
of carbon monoxide gas.
(j) sodium hydrogen carbonate effervesces when reacted with a dilute solution of
hydrochloric acid.
Q3.
Write ionic equations for each of the following reactions:
(a) dilute acetic acid reacts with a solution of potassium hydroxide.
(b) orthophosphoric acid reacts with a solution of barium hydroxide.
(c) solutions of nickel sulfate and ammonium carbonate are mixed.
(d) powdered aluminium reacts readily with warm dilute sulfuric acid.
(e) solutions of tin (II) chloride and sodium hydroxide are mixed.
2.
Mass-Mass stoichiometry
Q4. Calculate the mass of magnesium oxide formed when 2.431g of magnesium is burnt
in excess oxygen.
Q5. Calculate the mass of carbon dioxide released when one litre of octane undergoes
complete combustion in air according to the equation
2C8H18(l) + 25O2(g) -----> 16CO2(g) + 18H2O (l)
Note: density of octane = 0.785g.cm-3
Q6. Copper (II) nitrate decomposes on heating according to the equation
2Cu(NO3)2 (s) -----> 2CuO (s) + 4NO2 (g) + O2 (g)
After decomposition of a sample of copper nitrate, 3.6g of black copper oxide remains.
Calculate the original mass of copper nitrate required.
Q7. Assuming that limestone is 100% calcium carbonate, what mass of quicklime
(calcium oxide) will be produced by the thermal decomposition of 500g of limestone?
5
Q8. Potassium chromate reacts with potassium chloride, in the presence of concentrated
sulphuric acid, to form the deep red liquid chromyl chloride (Cr2O2Cl2), of density 1.935
g.cm-3. The equation for the reaction is as follows:
K2Cr2O7 + 4KCl + 3H2SO4 ----> 2 Cr2O2Cl2 + 3K2SO4 + 3H2O
Calculate the volume of chromyl chloride liquid formed from 6.25g of potassium
dichromate.
Q9. A 5.0 tonne charge of haematite ore (impure iron (III) oxide) undergoes reduction
within a blast furnace according to the equation
Fe2O3 (s) + 3CO (g) ----> 2Fe (l) + 3CO2 (g)
Calculate the percentage purity of the ore if 2.73 tonnes of iron is produced.
Q10. The sulfur content of coal may be estimated by igniting the sample of coal with
Na2CO3 and then, by suitable treatment, converting the sulfur present to a precipitate of
BaSO4. If, in a particular analysis, a 2.00g sample of coal yields 0.493g of barium sulfate,
what was the percentage by mass of sulfur in the coal?
Q11. A 1.233g sample of a mixture of NaBr and CdBr2 is treated with an excess of silver
nitrate solution, which precipitates all the Br- as AgBr. A mass of 1.910g of AgBr is
obtained. What is the percentage by mass of CdBr2 in the sample?
Hint: Let m(NaBr) = x g, then m(CdBr2) = (1.233 - x) g. This question is quite difficult!
3.
Mass-Volume stoichiometry
Q12. A sample of 8.655g of sulfamic acid (H2NSO3H) is dissolved in water and the
solution is carefully diluted to 100.00ml. What is the molarity of the solution?
Q13. Calculate the mass of zinc sulfate precipitated when 20.00ml of 0.45 M zinc nitrate
solution reacts with excess sulfuric acid.
Q14. What mass of sodium hydrogen carbonate will react exactly with 25.00 ml of
1.55M nitric acid according to the equation
NaHCO3 (s) + HNO3 (aq) ----> NaNO3 (aq) + H2O (l) + CO2 (g)
Q15. What volume of 0.20 M LiOH solution will exactly neutralise 35.9 ml of 0.11 M
sulfuric acid solution?
Q16. The reaction between copper and concentrated nitric acid can be represented by the
equation
Cu (s) + 4HNO3 (aq) ----> Cu(NO3)2 (aq) + 2NO2 (g) + 2H2O(l)
What volume of 14M HNO3 would be required to completely dissolve 8.4g of copper?
6
Q17. What mass of silver chloride will be precipitated when 25.0 ml of a solution
containing 0.50 M silver nitrate is reacted with 30.0 ml of 0.35 M sodium chloride
solution? Which reagent is in excess, and by how much (in grams)?
Q18. 45.0ml of 0.750 M AgNO3 solution is added to 65.0ml of 1.375 M Cr(NO3)3
solution. Calculate the resultant concentration of nitrate ions in the mixture.
Q19. A student is required to make up 250.0 ml of 0.200M nitric acid solution from a
stock supply of concentrated (14 M) acid. What volume of the concentrated acid will she
need to use, and what volume of water will need to be added?
4. Gas Volume calculations
Q20. Calculate the volume occupied by 4.4g of carbon dioxide gas at Standard
Laboratory Conditions. (Note: Vm = 24.5 L at S.L.C.)
Q21. Hydrogen peroxide decomposes over time to produce oxygen gas and water.
What volume of O2 (g) at S.T.P. will be produced by the complete decomposition of
200ml of 6.0 M H2O2 solution.
Q22. An oxygen cylinder of internal volume 6.65L contains oxygen gas under a pressure
of 16.7 MPa at a temperature of 28C.
(i) Calculate the mass of oxygen in the cylinder.
(ii) What volume would this gas occupy at 22C and 1.13 atm. pressure?
Q23. Propane is commonly used as the principle fuel in BBQ gas bottles. Given that a
9.0 kg gas bottle contains 85% propane which undergoes complete combustion according
to the equation
C3H8 (l) + 5O2 (g) ----> 3CO2 (g) + 4H2O (l)
Calculate the volume of CO2 produced at 35C and 98.6 kPa pressure.
Q24. Calculate the number of atoms of neon gas in a fluorescent tube of volume 3.21 L
and pressure 560 Pa at a temperature of 26C.
Q25. In the preparation of nitrogen monoxide by the reaction
3Hg (l) + 8HNO3 (aq) ----> 3Hg(NO3)2 (aq) + 2NO (g) + 4H2O (l)
24.7 g of mercury was treated with 180 ml of 6.0 M nitric acid. Calculate
(a) Which reagent is in excess and by how much (in grams)?
(b) What volume of NO is formed at S.T.P. ? (Note: Vm = 22.4 L at S.T.P.)
Q26. A gaseous compound of carbon and hydrogen contains 92.26% carbon. When
1.373g of the compound is collected at a temperature of 25C and a pressure of 99.485
kPa it is found to occupy a volume of 1.308 L. What is the molecular formula of the
compound?
7
Chapter Two Solutions
Q4. 4.031g Q5. 2424g Q6. 8.494g
Q7. 280g Q8. 4.54 ml
Q9. 78.1% Q10. 3.39% Q11. 20.4% Q12. 0.893 M
Q13. 1.453g Q14. 3.255g Q15. 39.5 ml
Q16. 37.8 ml
Q17. AgNO3 is in excess by 0.340g, m(AgCl) = 1.505g Q18. 2.744 M
Q19. 3.57 ml,
246.43 ml Q20. 2.45 L Q22. (i) 1420g, (ii) 950.6 L Q23. 1.355 x 104 L
Q24. 4.355 x 1020 Q25 a) HNO3 is in excess by 47.35g, b) 1.839 L Q26. CH, C2H2
Chapter 3 Questions
Q1.
Define the following terms:
a) acid
c) polyprotic
e) pH
g) volumetric analysis
i) secondary standard
k) endpoint
m) titre
o) ionisation
b) base
d) amphiprotic (amphoteric)
f) indicator
h) primary standard
j) equivalence point
l) titration
n) aliquot
p) dissociation
Q2.
Write the conjugate base of the following acids:
a) HCl
b) HNO3
c) H2SO4
d) NH4+
e) H2O
f) HOCl
g) CH3COOH
h) H2PO4i) HSO3j) HCN
Q3.
Write the conjugate acid of the following bases:
a) OHb) NH3
c) Cl
d) H2O
e) HPO42f) PO43g) HS
h) CO32i) O2j) NH2-
8
Q4.
For each of the following reactions, state whether the first named species is acting
as an acid, a base, or neither:
a) H2SO4 (aq) + 2NaOH (aq) ----> Na2SO4 (aq) + 2H2O (l)
b) BaCl2 (aq) + 2KOH (aq) ----> Ba(OH)2 (s) + 2KCl (aq)
c) 3NH3 (aq) + H3PO4 (aq) ----> (NH4)3PO4 (aq)
d) 2HCl (aq) + Zn (s) ----> ZnCl2 (aq) + H2 (g)
e) Ca(OH)2 (aq) + CO2 (g) ----> Ca(HCO3)2 (aq)
Q5.
Write equations to show the successive ionisations of the triprotic acid H3PO4
reacting with water.
Q6.
State whether each of the following species undergoes ionisation or dissociation
when added to water:
a) Mg(OH)2 (s)
b) KI (s)
c) HCl (g)
d) H2O (l)
e) CuSO4 (s)
f) HNO3 (l)
g) NaOH (s)
h) Na2Cr2O7 (s)
i) CH3COOH (l)
j) (NH4)2CO3 (s)
Q7.
250.0 ml of 0.0400 M limewater solution is prepared and through it is bubbled 75
cm-3 of CO2 (g) at S.T.P. Calculate the mass of calcium carbonate formed, according to
the equation
Ca(OH)2 (aq) + CO2 (g) ----> CaCO3 (s) + H2O (l)
Q8.
120.0 ml of 0.566 M nitric acid solution is exactly neutralised by 85.5 ml
potassium hydroxide solution. What is the concentration of the KOH solution?
Q9.
What volume of 2.088 M sulfuric acid is required to exactly neutralise a solution
made up of 100.0 g of sodium hydroxide pellets dissolved in 320.0 ml of water?
Q10. If V ml of 0.20 M NaOH is mixed with 2V ml of 0.80 M NaOH, what volume of
0.45 M H2SO4 would be required to effect neutralisation?
Q11. What volume of water would need to be added to 100.0ml of 0.354 M NaOH to
make the resulting solution 0.250 M NaOH?
Q12. What volume of 0.0641 M HClO4 solution would be required to make up 200.0
ml of 0.0250 M solution?
Q13. A laboratory technician wishes to make up 5.00 L of 0.450 M nitric acid solution
from a stock bottle of 14 M acid. What volume of the concentrated acid will he require?
What safety precautions should he adopt when diluting the concentrated acid?
9
Q14. Calculate the pH of each of the following solutions:
a) 0.010 M HNO3
b) 0.10 M HCl
-4
c) 1 x 10 M HNO3
d) 0.0050 M H2SO4
e) [H+] = 1 x 10-13 M
f) [H2SO4] = 5 x 10-6 M
Q15. Calculate the pH of the solution which results from bubbling 2.45 L of hydrogen
chloride gas at S.L.C. through 100 ml of water.
Q16. Calculate the pH of the solution which results from the dilution of 80.0 ml of 14
M HNO3 with 1040 ml of distilled water.
Q17. 5.89g of potassium hydroxide pellets are added to 28.00 ml of 0.625 M sulfuric
acid solution and the mixture is thoroughly stirred. Is the resultant solution acidic, basic
or neutral?
Q18. Calculate the pH of each of the following solutions:
a) [OH-] = 0.10 M
b) [NaOH] = 1 x 10-5 M
c) [KOH] = 1.0 M
d) [Mg(OH)2] = 5 x 10-4 M
e) [OH-] = 10-8.3 M
f) [LiOH] = 10 M
Q19. 2.00g of solid NaOH is carefully dissolved in 500 ml of water. Calculate the pH
of the resultant solution.
Q20.
Why can solid NaOH not be used to prepare a primary standard solution?
Q21. In order to accurately determine the concentration of a solution of potassium
hydroxide, a student intends to titrate it against 20.00 ml aliquots of a standard solution of
hydrochloric acid. Which one, or more, of the following procedures, is incorrect?
a) the pipette is first washed with water and then rinsed with the KOH solution.
b) the pipette is first washed with water and then rinsed with the HCl solution.
c) the burette is washed with water and then filled with the HCl solution.
Q22. A commonly used primary standard acid in analytical chemistry is potassium
hydrogen phthalate (KC8H5O4) - a monoprotic acid of molar mass 204.1 g.mol-1. In a
titration exercise it is found that a sample of 1.305g of potassium hydrogen phthalate
requires 17.28 ml of sodium hydroxide solution to neutralise it. What is the molarity of
the NaOH solution?
Q23. A 40.00 ml sample of vinegar containing acetic acid was diluted to 250.0ml in a
standard flask. A 20.00 ml aliquot of this solution required 27.35 ml of 0.0942 M NaOH
solution to reach endpoint. Calculate the percentage by mass of pure acetic acid in the
original vinegar sample. [Note: presume d (vinegar) = 1.00 g.cm-3]
10
Q24. A student carries out a volumetric analysis to determine the concentration of
hydrochloric acid in a sample of “spirits of salts” (a cleaning agent used to remove
cement from bricks). She carefully pours about 5 ml of the liquid into a 250.0 ml standard
flask and determines its mass to be 5.117g. Distilled water is slowly added to the flask
and the solution is agitated to ensure uniform mixing. 25.00 ml aliquots of this solution
are then pipetted into three separate volumetric flasks and 2-3 drops of methyl orange
indicator is added to each. Titration against a standard solution of 0.117 M Na2CO3
solution is carried out; the average titre volume required to reach endpoint being 17.83
ml. Calculate the concentration of HCl in the “spirits of salts” in
(a) g.L-1
(b) Molar concentration
[Note: presume d (spirits of salts) = 1.00 g.cm-3]
Q25. A student wishes to determine the percentage by mass of available nitrogen
(present as the ammonium ion) in a sample of commercially available lawn fertiliser. To
achieve this aim, he accurately weighs 1.556 g of fertiliser into a 250.0 ml standard flask
and makes it up to the mark with distilled water. 20.00 ml aliquots of this fertiliser
solution are then reacted with 25.00 ml of 0.1061 M NaOH solution, according to the
ionic equation
NH4+ (aq) + OH- (aq) ----> NH3 (g) + H2O (l)
The excess OH- is then titrated against 0.119 M HCl solution, the average titre
required being 12.07 ml.
Calculate the percentage by mass of nitrogen in the fertiliser.
Solutions to Chapter 3 questions
Q2. a) Clb) NO3g) CH3COO-
c) HSO4h) HPO42-
d) NH3
i) SO32-
e) OHj) CN-
f) OCl-
Q3. a) H2O b) NH4+
g) H2S
c) HCl
h) HCO3-
d) H3O+
i) OH-
e) H2PO4j) NH3
f) HPO42-
Q4. a) acid
c) base
d) neither
e) base
b) neither
Q5.
H3PO4 (aq) + H2O (l) ----> H2PO4- (aq) + H3O+ (aq)
H2PO4- (aq) + H2O (l) ----> HPO42- (aq) + H3O+ (aq)
HPO42- (aq) + H2O (l) ----> PO43- (aq) + H3O+ (aq)
Q6.
a) dissociation
e) dissociation
i) ionisation
b) dissociation
f) ionisation
j) dissociation
c) ionisation
g) dissociation
d) ionisation
h) dissociation
11
Q7. 0.335 g
Q8. 0.794 M
Q9. 0.59 L
Q11. 41.6 ml
Q12. 78.00 ml
Q13. 161 ml
c) 4
d) 2
Q18. a) 13
e) 13 f) 5
b) 9
Q10. 2 V ml
Q14. a) 2
b) 1
Q15. 0Q16. 0Q17. alkaline
c) 14 d) 11 e) 5.7 f) 15
Q19. 13
Q20. NaOH is hydroscopic and reacts with CO2 from atmosphere
Q21. (b) is correct
Q22. 0.370 M
b) 8.15 M
Q25. 17.58 %
Q23. 4.83 %
Q24. a) 297 g.L-1
Chapter 4 questions
Q1.
Calculate the oxidation number of the underlined element for each of the
following species:
a) O2
b) SO3
c) Fe(NO3)3
d) MnO4e) CrO2
f) Na2B4O7
g) Zn(BrO3)2
h) Ga2(CO3)3
i) PbI4
j) SnSO4
k) H3PO4
l) Mg3(AsO4)2
Q2.
Calculate the oxidation number of sulfur in each of the following species:
a) SO2
b) H2SO4
c) H2S
2d) SO3
e) S2
f) S2O32-
Q3.
Calculate the oxidation number of nitrogen in each of the following species:
a) NO
b) NO2
c) N2
d) HNO2
e) HCN
f) N2O4
g) NO3h) N2O
i) NH3
Q.4
For each of the following redox reactions, state which species is acting as the
oxidant and which as the reductant:
a) Cl2(g) + Zn (s) ----> Zn2+ (aq) + 2Cl- (aq)
b) 2Li (s) + 2H2O (l) ----> 2LiOH (aq) + H2 (g)
c) Fe2O3 (s) + 3H2 (g) ----> 2Fe (s) + 3H2O (l)
d) 2H2S (g) + SO2 (g) ----> 3S (s) + 2H2O (l)
e) HNO2 (aq) + H2O2 (aq) ----> HNO3 (aq) + H2O (l)
Q5.
Write partial ionic equations for each of the following:
a) iodide ions are oxidised to iodine
b) nitric acid is reduced to nitrogen dioxide
c) vanadate ions (VO32-) are reduced to vanadium (III) ions
d) sulfur is oxidised to thiosulfate ions (S2O32-)
12
e) methanol (CH3OH) is oxidised to methanal (HCHO)
f) sulfite ions (SO32-) are reduced to hydrogen sulfide (H2S)
Q6.
Write overall ionic equations for the following redox reactions:
a) A strip of magnesium metal displaces silver metal from a solution of AgNO3 and is
itself dissolved.
b) Concentrated nitric acid reacts with silver metal to produce Ag+ ions and nitrogen
dioxide gas, among other products
c) When sulfur dioxide gas is bubbled through an acidified solution of potassium
dichromate, the SO2 is oxidised to SO42- and the Cr2O72- is reduced to Cr3+ ions.
d) A solution of potassium permanganate is decolourised by the addition of excess oxalic
acid (H2C2O4). CO2 and Mn2+ are among the products of the reaction.
e) Hydrogen peroxide spontaneously decomposes over a period of time to produce water
and oxygen gas
Q7.
The reaction which occurs within the common Leclanché dry cell may be
represented by
2MnO2 (s) + Zn (s) + NH4+ (aq) ----> Mn2O3 (s) + Zn2+ (aq) + 2NH3 (aq)
(i) Which species is acting as the oxidant and which as the reductant?
(ii) What mass of MnO2 would be required to react completely with 15.0g of
zinc?
Q8.
Calculate the mass of powdered zinc metal that would be required to displace all
of the Ag+ ions from 5.0 L of waste photographic emulsion solution as silver metal,
according to the equation
2Ag+ (aq) + Zn (s) ----> 2Ag (s) + Zn2+ (aq)
Presume [Ag+] = 120 ppm and d (waste solution) = 1.00 g.cm-3
Q9.
18.22 ml of a solution of potassium permanganate exactly reacts with 0.605 g of
nickel metal; Mn2+ and Ni2+ being among the products. Calculate the concentration of the
KMnO4 solution.
Q10. 8.27 ml of 2.25 M sulfuric acid precisely oxidises 15.0g of an impure sample of
iron; SO2 and Fe2+ being among the products. Presuming iron is the only substance
undergoing oxidation, what is the percentage purity of iron in the sample?
Q11. A 0.2817g sample of iron ore was dissolved in acid and all of the Fe present was
converted to Fe2+ ions. The resulting Fe2+ solution was titrated with 0.01864 M K2Cr2O7
solution, a titre volume of 21.24 ml being required to reach endpoint; Fe3+ and Cr3+ being
among the products. Calculate the percentage of iron in the iron ore sample.
Q12. A student wishes to verify the mass of active constituent (ascorbic acid, C6H8O6)
in a 250 mg tablet of Vitamin C. She weighs the tablet and records the mass as 0.344g.
She then dissolves the tablet in about 50 ml of deionised water in a conical flask. This
13
solution is then titrated against a 0.0528 M solution of iodine, using starch as indicator. A
titre volume of 27.18 ml was required to reach endpoint.
The equation for this reaction may be written as:
C6H4O2(OH)4 (aq) + I2 (aq) ----> C6H4O4(OH)2 (aq) + 2H+ (aq) + 2I- (aq)
(a) Calculate the mass of ascorbic acid in the tablet (in mg).
(b) What possible functions may the substances perform which make up the
remainder of the tablet’s mass?
Q13. Household bleach contains the strong oxidant ‘sodium hypochlorite’, NaOCl, as
the active ingredient. The concentration of NaOCl is generally known as the ‘available
chlorine’ and is often expressed as the mass of active ingredient per unit volume of
solution, or w/v.
A student wishes to verify the available chlorine content in a sample of commercially
available bleach, quoted as ‘40g/L available chlorine’.
To achieve this aim he pipettes 25.00ml of the bleach into a 250.0 ml standard flask and
makes up to the mark with deionised water. He then pipettes three 20.00 ml aliquots of
this diluted solution into separate conical flasks and adds about 10 ml of acidified
potassium iodide solution. He notes that the solution in the flask immediately becomes
dark brown, as the available chlorine oxidises the iodide ions to iodine, according to the
equation:
OCl- (aq) + 2I- (aq) + 2H+ (aq) -----> I2 (aq) + Cl- (aq) + H2O (l)
He then titrates this solution with a standard solution of 0.0513 M sodium thiosulfate
solution for each flask; an average titre volume of 9.57 ml being required. The relevant
equation is:
I2 (aq) + 2S2O32- (aq) ----> S4O62- (aq) + 2I- (aq)
(i) Calculate the no. of mol of S2O32- in each flask.
(ii) Calculate the no. of mol of I2 reduced by the S2O32- ions in each flask.
(iii) Deduce the no. of mol of OCl- in the aliquot of diluted solution.
(iv) Calculate the no. of mol of OCl- in the original sample of bleach.
(v) Thus deduce the no. of mol of chlorine atoms (as Cl-) in the original sample
of bleach.
(vi) Calculate the mass of available chlorine in the original sample, and thus
determine the w/v ratio (Presume d (bleach solution) = 1.00 g.ml-1).
Q14. A scientist wishes to determine the percentage by volume of alcohol in a bottle of
Chilean wine. She dispenses a 20.00 ml sample of the wine into a 250.0 ml standard flask
and makes it up to the mark with deionised water. She then withdraws a 20.00 ml aliquot
of this mixture and adds to it precisely 20.00 ml of 0.05279 M K2Cr2O7 and
approximately 10 ml of 8M H2SO4. After heating this acidified mixture carefully for 10
minutes all of the alcohol in the wine has been oxidised to ethanal by the excess
dichromate, according to the equation:
3CH3CH2OH (aq) + Cr2O72- (aq) + 8H+ (aq) ----> CH3CHO (aq) + 2Cr3+ (aq) + 7H2O (l)
14
The solution is then allowed to cool, about 2g of potassium iodide is added and the
excess Cr2O72- oxidises the iodide ions to iodine, according to the equation:
Cr2O72- (aq) + 14H+ (aq) + 6I- (aq) ----> 2Cr3+ (aq) + 7H2O (l) + 3I2 (aq)
Finally, the iodine thus formed is titrated against a standard solution of 0.1091 M sodium
thiosulfate solution, an average titre of 7.72 ml being required to reach endpoint. The
relevant equation is:
I2 (aq) + 2S2O32- (aq) ----> S4O62- (aq) + 2I- (aq)
(i) Calculate the no. of mol of S2O32- in the titre.
(ii) Calculate the no. of mol of I2 reduced by the S2O32- ions in each flask.
(iii) Calculate the no. of mol of Cr2O72- in excess.
(iv) Calculate the no. of mol of Cr2O72- required to oxidise the ethanol in the
aliquot.
(v) Calculate the no. of mol of ethanol in the aliquot.
(vi) Calculate the mass of ethanol in the original sample.
(vii) Given that the density of ethanol = 0.785 g.ml-1, determine the % volume of
alcohol (% v/v) in the wine.
Solutions to Chapter 4 questions
Q1. a) 0
g) +5
b) +6
h) +3
c) +3
i) +4
d) +7
j) +2
e) +4
k) +5
f) +3
l) +5
Q2. a) +4
b) +6
c) -2
d) +4
e) 0
f) +2
Q3. a) +2
g) +5
b) +4
h) +1
c) 0
i) -3
d) +3
e) -3
f) +4
Q4.
a) oxidant is Cl2, reductant is Zn
b) oxidant is H2O, reductant is Li
c) oxidant is Fe2O3, reductant is H2
d) oxidant is SO2, reductant is H2S
e) oxidant is H2O2, reductant is HNO2
Q5.
a)
b)
c)
d)
e)
f)
Q6.
a) Mg (s) + 2Ag+ (aq) ----> Mg2+ (aq) + 2Ag (s)
b) HNO3 (aq) + H+ (aq) + Ag (s) ----> NO2 (g) + Ag+ (aq) + H2O (l)
2I- (aq) ----> I2 (aq) + 2e
HNO3 (aq) + H+ (aq) + e ----> NO2 (g) + H2O (l)
VO32- (aq) + 6H+ (aq) + e ----> V3+ (aq) + 3H2O (l)
2S (s) + 3H2O (l) ----> S2O32- (aq) + 6H+ (aq) + 4e
CH3OH (aq) ----> HCHO (aq) + 2H+ (aq) + 2e
SO32- (aq) + 8H+ (aq) + 6e ----> H2S (g) + 3H2O (l)
15
c) Cr2O72- (aq) + 2H+ (aq) + 3SO2 (g) ----> 2Cr3+ (aq) + H2O (l) + 3SO42- (aq)
d) 2MnO4- (aq) + 6H+ (aq) + 5H2C2O4 (aq) ----> 2Mn2+ (aq) + 8H2O (l) +
10CO2 (g)
e) 2H2O2 (aq) ----> 2H2O (l) + O2 (g)
Q7.
(i) oxidant is MnO2, reductant is Zn
(ii) 39.9g
Q8. 0.182g
Q9. 0.226 M
Q10. 69.3%
Q12. a) 253 mg b) flavour, colour, binding agents
(ii) 2.455 x 10-4 mol (iii) 2.455 x 10-4 mol
(vi) 1.088g, 43.5g.L-1
(iii) 1.404 x 10-4 mol
Q13. (i) 4.909 x 10-4 mol
(iv) 0.0307 mol
Q14. (i) 8.423 x 10-4 mol
(iv) 9.154 x 10-4 mol
Q11.47.1%
(v) 0.0307 mol
(ii) 4.211 x 10-4 mol
(v) 0.0343 mol
(vi) 1.580g
(vii) 10.06%
Chapter 5 questions
Q1.
Suggest an analytical procedure that could be employed in each of the following
situations:
(i) a laboratory technician wishes to determine whether a white crystalline solid
is NaCl or Sr(NO3)2.
(ii) a doctor suspects an unconscious patient may have taken an overdose of
barbiturates
(iii) a metallurgist wishes to analyse the mineral content of a sample of ore to
measure the proportion of nickel present
(iv) an E.P.A. officer analyses a water sample to test for the presence of lead.
(v) an Agricultural scientist wishes to determine which oils are present in the
leaves of a particular species of eucalypt.
(vi) a quality control officer at a large perfumery suspects a cheap and inferior
shipment of essential oils has been delivered.
(vii) a team of engineers working on the McLaren F1 racing team wish to check
the assay of metals used in a gearbox housing
(viii) a student wants to separate the components of the dyes used in fluorescent
marker pens
(ix) a food chemist is required to ensure the amount of iron added to a particular
brand of breakfast cereal is within prescribed limits.
(x) a medical scientist is attempting to identify the formula of a large enzyme
suspected of playing a role in the body’s response to the H.I.V. virus
16
Q2.
A student wished to separate the coloured dyes used in a packet of ‘smarties’ by
employing paper chromatography. He moistened a blue, red and purple smartie with
water and spotted the colours onto a strip of chromatography paper. The paper was then
dipped into a solvent solution of butan -1-ol, ethanol and 2% ammonia and allowed to
develop over 2 hours.
After this period of time, the student measured the distance moved by the solvent and
each coloured component of the dyes up the paper. The results were as follows:
Blue smartie: yellow component 3.2 cm, blue component 6.7 cm
Red smartie: orange component 4.5 cm, red component 5.8 cm
Purple smartie: red component 6.0 cm, yellow component 3.3 cm, blue
component 5.3 cm
The solvent front had moved 18.3 cm
(i) How many different chemical dyes were used to produce the blue, red and purple
smarties?
(ii) Calculate the Rf value for each separate component.
Q3.
Determine the concentration (in microgram per litre) of an unknown glucose
solution by first constructing a calibration curve for a set of solutions of known
concentration. The glucose solutions were first reacted with an arsenomolybdate
compound to form a blue complex which could be detected using a colorimeter. The
results are as follows:
Solution Number Conc. of glucose (g.L-1) Spectrophotometer reading
Blank
0
0.000
1
50
0.097
2
100
0.194
3
150
0.289
4
200
0.385
5
250
0.483
unknown
?
0.348
Q4.
An environmental officer wished to test a water sample from a creek for
phosphate content. It is known that excess phosphate concentration, generally from
fertiliser run-off, can contribute to the eutrophication of the waterway. To perform the
test she generates a calibration curve by making up a series of solutions of known
phosphate concentration. These solutions are then reacted with ammonium molybdate,
ammonium vanadate and concentrated nitric acid to generate a yellow molybdenum
vanadatophosphoric acid complex which could be tested with a colorimeter. The Officer
tested both an unknown solution and the creek water sample for phosphorus (as
phosphate) content. The results are as follows:
17
Solution Number
Blank
1
2
3
4
unknown
creek water
Concentration of
phosphorus (ppm)
0
2.5
5.0
7.5
10.0
?
?
Spectrophotometer reading
0.000
0.174
0.346
0.518
0.690
0.465
0.012
Construct a calibration curve and so determine the concentration of phosphorus (as
phosphate) in both the unknown solution and the creek water.
Q5.
Iron is an essential element in our diet; it forms an integral part of haemoglobin,
myoglobin and many enzymes, and can be found in meat, egg yolks and legumes (such as
peas). A food scientist wished to analyse a sample of canned peas to determine the iron
content, using Atomic Absorption Spectroscopy.
To do this, he first made up a series of standard solutions of iron content between 1 and
10 ppm. He then dissolved a 5.13g sample of peas in 40 ml of 8 M hydrochloric acid to
break down the organic matter and liberate all of the available iron. The solution was then
filtered and made up to 50.0 ml with deionised water. The absorbency of all solutions
was then recorded on the AAS; results were as follows:
Solution Number
Deionised water
1
2
3
4
5
canned peas
Concentration of iron
(ppm)
0
1.0
3.0
5.0
7.0
8.0
?
Absorbency reading
0.002
0.020
0.056
0.092
0.127
0.143
0.048
a) Construct a calibration curve and so determine the concentration of iron (in ppm) in
the sample.
b) Determine the mass of iron (in g) per gram of canned peas in the sample.
[Presume density of solution = 1.00 g.ml-1]
Q6.
Chromium is an undesirable contaminant of water supplies due to its toxic nature:
chromium is a suspected carcinogen. Levels of chromium of 0.003 mg.L-1 in water
supplies indicate the presence of industrial wastes. Were the concentrations of chromium
to rise to 0.05 mg.L-1, the water would not be fit for human consumption.
18
A sample of water is analysed using a graphite flame AAS (capable of measuring
concentrations to parts per billion) and its absorbency is recorded. A set of standard
solutions of varying concentrations of chromium solutions is also analysed; the results are
presented below:
Solution Number
Concentration of
chromium (ppb)
0
0.20
0.40
0.60
0.80
0.10
?
Deionised water
1
2
3
4
5
unknown
Absorbency reading
0.001
0.047
0.092
0.136
0.187
0.226
0.066
a) Construct a calibration curve and so determine the concentration of chromium (in ppb)
in the sample.
b) Convert this concentration value from ppb to mg.L-1. Is the water supply
contaminated?
c) If a person were to drink a 300ml glass of water contaminated with chromium of
concentration 85 ppb, what mass of chromium would he ingest?
[Density of water = 1.00 g.ml-1]
Solutions to Chapter 5 questions
Q1. (i) flame test
(ii) HPLC
(v) HPLC
(vi) GLC
(ix) colorimetry/AAS
(iii) AAS
(vii) AAS
(x) HPLC
(iv) AAS/colorimetry
(viii) paper chromatography
Q2. (i) 5, (ii) yellow = 0.18, blue1 = 0.37, orange = 0.25, red = 0.32, blue2 = 0.29
Q3. 180 g.ml-1
Q4. unknown = 6.7 ppm, creek water = 0.17 ppm
Q5. a) 0.38 ppm, b) 3.7 g
Q6. a) 2.28 x 10-4 mg.L-1, b) no c) 3.5 = 10-9 g
19
Chapter 6 questions
Q1.
Write the expression for the equilibrium constant for each of the following
equations:
a) PCl5 (g)  PCl3 (g) + Cl2 (g)
b) CaCO3 (s) + 2HCl (aq)  CaCl2 (aq) + CO2 (g) + H2O (l)
c) 2H2O (l) + O2 (g)  2H2O2 (l)
d) CH3COOH (l) + CH3OH (l)  CH3COOCH3 (l) + H2O (l)
e) NH4COONH2 (s)  2NH3 (g) + CO2 (g)
f) 5B2H6 (g) + 2BCl3 (g)  6B2H5Cl (g)
Q2.
An equilibrium mixture of H2, I2 and HI at 500 C is determined to have
concentrations of 2.58 M, 2.41 M and 16.05 M respectively. Calculate the equilibrium
constant for the decomposition reaction:
2HI (g)  H2 (g) + I2 (g)
Q3.
Calculate the equilibrium constant for the reaction
2NO (g) + Cl2 (g)  2NOCl (g), given that
[NOCl]eq = 1.7074 M, [NO]eq = 2.3505 x 10-3 M and [Cl2]eq = 7.9266 x 10-4 M
Q4.
Given that the equilibrium constant for the reaction
4HCl (g) + O2 (g)  2H2O (g) + 2Cl2 (g) ; Kc = 3.152 x 103 M-1 at 400 C
calculate the equilibrium constant for the reactions
1
(i) 2HCl (g) +
O2 (g)  H2O (g) + Cl2 (g) at 400 C
2
1
(ii) H2O (g) + Cl2 (g)  2HCl (g) +
O2 (g) at 400 C
2
Q5.
For the reaction
H2 (g) + I2 (g)  2HI (g) ; Kc = 48.5 at 730 K
Calculate the [I2] at equilibrium given that the equilibrium concentrations of H2 and HI
are 1.696 x 10-3 M and 1.181 x 10-2 M respectively.
Q6.
Given that
N2 (g) + 3H2 (g)  2NH3 (g) ;
Kc = 0.58 M-2 at 400 C
a) Calculate the [H2] at equilibrium given that [N2]eq = 0.0381 M and [NH3]eq =
0.1096 M at the same temperature.
b) Would the value of the equilibrium constant increase, decrease or remain
constant with an increase in temperature to 600 C, given that the forward reaction is
exothermic?
20
Q.7
A mixture of SO2 (g) and O2 (g) was allowed to come to equilibrium in a 1.4 L
vessel. Analysis of the resulting contents showed 0.42 mol of SO2, 0.28 mol of O2 and
0.35 mol of SO3. Calculate the equilibrium constant for the reaction:
2SO2 (g) + O2 (g)  2SO3 (g)
Q8.
Consider the reversible reaction
2P (g) + Q (g)  5R (g) + 3S (g)
If, at equilibrium at a certain temperature, the concentrations of the species are
as follows:
[P] = 0.0573M, [Q] = 0.0228 M, [R] = 0.828 M and [S] = 0.695 M
calculate the equilibrium constant at this temperature.
Q9.
0.600 mol of N2O4 (g) is introduced into an evacuated 2.00 L vessel and allowed
to reach equilibrium according to the equation:
N2O4 (g)  2NO2 (g)
At equilibrium, 0.14 mol of N2O4 remains. Calculate the equilibrium concentrations of
both NO2 and N2O4 and consequently calculate the equilibrium constant for the reaction
at this temperature.
Q10. Into an evacuated vessel of volume 10.0 L at 700 K is introduced 1.5 mol of CO
(g) and 0.5 mol of Cl2 (g). When the reaction reaches equilibrium, it is determined that
[COCl2] = 0.0485 M. Calculate the equilibrium concentrations of CO and Cl2 and so
determine the equilibrium constant for the reaction at this temperature. The equation is:
CO (g) + Cl2 (g)  COCl2 (g)
a) Define Le Chatelier’s Principle.
b) Explain the difference between the position of equilibrium and the equilibrium
constant. State the three macroscopic properties that can affect the position of
equilibrium. Only one of these can affect the equilibrium constant; which one?
Q11.
Q12. What would be the effect on the extent of forward reaction in each of the
following cases if hydrogen were added to the reaction system:
a) N2 (g) + 3H2 (g)  2NH3 (g)
b) 2HBr (g)  H2 (g) + Br2 (g)
c) CO (g) + H2O (l)  CO2 (g) + H2 (g)
d) 2B2H6 (g)  B4H10 (g) + H2 (g)
e) Fe3O4 (s) + H2 (g)  3Fe (s) + 4H2O (g)
Q13.
What would be the effect on the position of equilibrium for the reaction
Zn2+ (aq) + NH3 (aq)  Zn(NH3)2+ (aq) ;  H = -ve
in each of the following cases:
a) addition of a small volume of NH3
21
b) removal of a small amount of Zn2+
c) dilution of the system by the addition of deionised water
d) the system is heated on a water bath
Q14.
What, if any, will be the effect on the position of equilibrium for the reaction
H2S (g)  2H2 (g) + S2 (g)
of the addition of inert nitrogen gas to the reaction vessel?
Q15.
For the reaction
N2O4 (g)  2NO2 (g) ;  H = -ve
predict the effect on (i) the position, and
(ii) the equilibrium constant of the following changes:
a) addition of NO2 (g)
b) decrease in temperature
c) increase in pressure
Q16. Given the following information:
HCl (g) + H2O (l)  H3O+ (aq) + Cl- (aq), Kc = 5.5 x 108 at 25 C
CH3COOH (l) + H2O (l)  H3O+ (aq) + CH3COO- (aq), Kc = 9.9 x 10-4 at 25 C
explain the difference in relative strengths of hydrochloric and acetic (ethanoic) acids.
Q17.
The pH scale is based on the ionisation product of water
Kw = [H3O+][ OH-] = 10-14 at 25 C
which itself is based on the reaction described below:
H2O (l) + H2O (l)  H3O+ (aq) + OH- (aq)
This reaction is endothermic in the forward reaction.
At 25 C, the pH of pure water is 7.
(i) Predict the effect on the position of equilibrium of cooling the water to 10 C.
(ii) Will the pH of the water increase, decrease or remain the same?
(iii) Will the water become acidic, basic or remain neutral? Explain your answers.
Q18.
An important reaction in the production of sulfuric acid is
2SO2 (g) + O2 (g)  2SO3 (g) ;  H = -197 kJ mol-1
An engineer wishes to produce the maximum yield of SO3 (g) possible. Ignoring such
factors as cost and rate of reaction, explain how the engineer may alter the conditions of
temperature, pressure and concentration to maximise product yield.
Q19. Faulty exhaust pipes can lead to carbon monoxide gas entering the passenger
cabin of motor vehicles, leading to driver drowsiness and the possibility of an accident.
22
(i) By writing suitable equations, explain how carbon monoxide competes with
oxygen in its reaction with haemoglobin in the bloodstream.
(ii) Why does carbon monoxide poisoning cause drowsiness and, eventually,
death?
(iii) How may carbon monoxide poisoning be treated by doctors? Use relevant
equations in your explanation.
Q20. The cold ocean waters of the Antarctic hold considerably more dissolved oxygen
than the much warmer water of the tropics; a contributory factor in why Antarctic waters
are capable of sustaining a much greater biomass of marine creatures. Based on this fact,
would the reaction
H2O
 O2 (aq)
O2 (g) 
be endothermic or exothermic in the forward direction?
Q21. Phenolphthalein is a common acid/base indicator which changes from a pink-red
colour in alkaline solutions to colourless in acidic environment. The reaction of
phenolphthalein and its conjugate may be represented as:
HPh (aq) + H2O (l)  Ph- (aq) + H3O+ (aq)
(i) Which direction does the reaction proceed on addition of an acidic solution?
(ii) Which form of phenolphthalein, the acid HPh or its conjugate base, Ph-, is the
coloured form?
Q22. Bromocresol green (tetrabromophenol m-cresosulfonphthalein) is an acid/base
indicator which changes from yellow to blue. The reaction may be represented as:
HBrG (aq) + H2O (l)  BrG- (aq) + H3O+ (aq)
Given that the HBrG (aq) form of the indicator is yellow, what colour will the indicator
exhibit in acid solution?
Q23. Explain the importance of buffer systems in the human body. Using the example
of the H2CO3 (aq)/HCO3- (aq) + H+ (aq) buffer, explain how the body counters small
variations in pH.
Solutions to Chapter 6
Q1. a) Kc =
c) Kc =
 PCl3 Cl2 
 PCl5 
 H 2 O2 2
 H 2 O2 O2 
b) Kc =
CaCl2 CO2  H2O
CaCO3  HCl 2
d) Kc =
CH3COOCH3  H 2 O
CH3COOH CH3OH 
23
e) Kc =
 NH3 2 CO2 
f) Kc =
 NH4COONH2 
Q2. Kc = 0.0241
 B2 H5Cl 
 B2 H 6 5  BCl3 2
Q3. Kc = 8.3993 x 1011 M-1
(ii) Kc = 1.78 x 10-2 M-1
Q5. 1.696 x 10-3 M
Q7. 3.47 M-1 Q8. 1.745 x 103 M5
Q4. (i) 56.1 M-1,
Q6 a) 0.816 M b) decrease
Q9. [N2O4] = 0.0700 M, [NO2] = 0.460 M,
Kc = 3.02 M Q10. [CO] = 0.1015 M, [Cl2] = 0.0015 M, Kc = 319 M-1
Q11 b) temperature (both), pressure and concentration
Q12 a) increase b) decrease, c) decrease, d) decrease,
Q13 a) right,
b) left
b) i) right, ii) increase
iii) neutral
c) left
24
Q14. no effect
c) i) left, ii) no effect
Q15 a) i) left, ii) no effect
Q17 a) i) left, ii) increase
Q18. decrease temperature, increase pressure, add excess reactants
and/or remove product as it forms
Q22. yellow
d) left
e) increase.
Q20. exothermic
Q21. left, Ph- is coloured