Download Homework Exercises

S4 UNIT 1:
CHEMICAL CHANGES AND STRUCTURES
Homework 1 : Rates of Reaction
1. What happens to the rate of a reaction if the temperature is increased?
(1)
2. What happens to the rate of a reaction if the concentration of the reactants is
decreased?
(1)
3. What happens to the rate of a reaction if the surface area of a reactant is decreased?
(1)
4. Give four ways in which you could speed up the rate of a reaction.
(4)
5. How can the rate of a chemical reaction be measured?
(1)
6. Sodium carbonate reacts with hydrochloric acid to form carbon dioxide.
Brian set up the experiment and measured the volume of carbon dioxide given off over a
period of time and recorded his results.
Time (s)
0
10
30
40
50
60
70
Volume of carbon
Dioxide / cm3
0
12
29
34
36
37
37
(a) Draw a labelled diagram of the apparatus he could have used to carry out this
experiment.
(3)
(b) Draw a line graph on graph paper of his results.
(3)
(c) Suggest a value for the volume of carbon dioxide collected during the first 20
seconds.
(1)
(d) Calculate the rate when the volume of gas collected is 30cm3
(2)
(e) Write the formula for sodium carbonate.
(1)
(f) Describe the test for Carbon dioxide gas and the result you would expect.
(2)
(20)
Chemical Changes and Structure
Homework 2: Formulae and Equations
1. Write formulae for the following compounds:
(a)
(b)
(c)
(d)
(e)
(f)
2.
Potassium oxide
Aluminium iodide
Hydrogen sulphide
Magnesium hydroxide
Ammonium sulphate
Silver (I) oxide
(6)
Sulphuric acid, H2SO4 reacts with ammonia, (NH3) to form ammonium sulphate, (NH4)2SO4.
(a) Write the word equation for this reaction.
(b) Write a balanced symbol equation.
(c) In the balanced equation, how many atoms are there in the reactants.
(1)
(1)
(1)
3. Balance this equation for the reaction of glucose (C6H12O6) with oxygen:
C6H12O6 + O2 ⟶
CO2 + H2O
(1)
(10)
Chemical changes and Structure:
Homework 3: Formulae and Equations
1.
Write formulae for the following compounds:
(a) Mercury (II) chloride
(b) Copper (I) bromide
(c) Iron (III) oxide
(d) Gold (II) chloride
(e) Manganese (IV) oxide
2. Balance each of the following equations.
(a) Li +H2O ⟶ LiOH + H2
(b) Fe + O2 ⟶ Fe2O3
(c) CaCO3 +HCl ⟶ CaCl2 + H2O + CO2
(d) N2 + H2 ⟶ NH3
(e) Ca + H2O ⟶ Ca(OH)2 +H2
(5)
(5)
(10)
Chemical changes and Structure:
Homework 4: Bonding
1. Give the name and formula of
(a)
a diatomic element.
(b)
a diatomic compound
(4)
2. Element X has a melting point greater than 12000C. A chloride of this element is a solid at
room temperature. Which of the following could be Element X?
A
B
C
D
Hydrogen
Sulphur
Carbon
Copper
(1)
3. Copy and complete the table below :
Bonding and Structure
Metallic
Ionic
Covalent network
Covalent molecular
Example of substance
(4)
4. Draw diagrams to show the shape of
(a)
(b)
(c)
(d)
Water
Ammonia
Methane and
Hydrogen fluoride molecules
,
5. (a) What is meant by a covalent bond?
(b) Draw a diagram showing all the electrons involved for
(4)
(1)
(i) NCl3
(ii) H2S
(4)
6. Write ionic formulae for
(a)
aluminium nitrate
(b)
magnesium chloride
(2)
(20)
Chemical changes and Structure:
Homework 5: Mole calculations
1. What is the mass of
(a) 1 mol of sodium atoms
(b) 0.5 mol of oxygen atoms
(c) 3 mol of oxygen molecules O2
(d) 0.25 mol of sulphur atoms
(e) 2.5 mol of sulphur molecules S8
(10)
2. Find the number of moles present in
(a) 64g of lead
(b) 14g of iron
(c) 40g of hydrogen (H2)
3. How many grams are in
(a) 0.5 mol Ca(OH)2
(b) 0.1 mol H2SO4
(6)
(4)
(20)
Chemical changes and Structure:
Homework 6: Concentration calculations
1. Calculate the number of moles in 50cm3 of 0.25moll-1 solution
(1)
2. Calculate the mass of sodium nitrate required to prepare 2 litres of
0.01 moll-1 solution.
(2)
3. Calculate the number of moles in 150cm3 of a 0.2mol l-1 magnesium
hydrogencarbonate solution.
(1)
4. Calculate the mass of ammonium nitrate required to prepare 50 cm3
of a solution of concentration 0.9 moll-1.
(3)
5. Calculate the concentration of a solution of sodium hydroxide (NaOH)
made when 0.24g is dissolved in water and made up to 400cm3.
(3)
(10)
Chemical changes and Structure:
Homework 7: Percentage composition and empirical formulae.
1. Calculate the percentage by mass of :
(a) Carbon in ethane C2H6
(b) Nitrogen in ammonia (NH3)
(c) Oxygen in calcium nitrate Ca(NO3)2
(6)
2. Calculate the percentage, by mass, of all the elements in:
3.
(a) Ammonium chloride NH4Cl
(b) Sucrose C12H22O11
(4)
Determine the empirical formula of the following compound from
the masses of the elements present.
Sulphur 2g
Oxygen 3g
(4)
4. (a) A hydrocarbon was found to contain 85.71% by mass of carbon.
Determine the empirical formula of the hydrocarbon.
(b) Given that the formula mass of the hydrocarbon is 70, determine
its molecular formulae.
(4)
(2)
(10)
Chemical changes and Structure:
Homework 8: Acids and alkalis.
1.
(a)
(b)
(c)
(d)
2.
(a)
(b)
(c)
3.
What is meant by an alkali?
Give an example of an alkali.
What happens to the OH-(aq) concentration of an alkali when it
is diluted?
What happens to the pH of an alkali when it is diluted?
(1)
(1)
What is the general word equation for an acid reacting with an alkali?
Write a word equation for sodium hydroxide reacting with
sulphuric acid.
Write a balanced formula equation for this reaction.
(1)
(1)
(1)
(1)
(1)
Which of the following oxides dissolve in water to give a solution with pH
greater than 7?
(a)
(b)
(c)
(d)
Na2O
Al2O3
SO2
AgO
(1)
4.
H2O(l)
H+(aq) + OH-(aq)
(a) What is the pH of water?
(b) Explain how it has this value.
(1)
(2)
5.
(a) What is the pH of a 0.01 moll-1 solution of HCl?
(b) What is the pH of a 0.01 moll-1 solution of NaOH?
(1)
(1)
6.
Copper chloride can be made by reacting excess copper (II) carbonate with hydrochloric acid.
Copper (II) carbonate + hydrochloric acid ⟶ copper(II)chloride + water + X
(a)
(b)
(c)
(d)
Name substance X
Write a balanced equation for the reaction
What is meant by an excess of one chemical in a chemical reaction?
When the reaction is finished, unreacted copper(II) carbonate would be
left in the beaker. What else would be observed indicating that the reaction
is over?
(e) Draw a labelled diagram of the apparatus you would use to remove the
unreacted copper carbonate from the solution.
(1)
(2)
(1)
(1)
(2)
(20)
Chemical changes and Structure:
Homework 9: Ionic Formulae and Titrations
1.
Write the ionic formulae for:
(a)
(b)
(c)
(d)
2.
(4)
Iron reacts with dilute hydrochloric acid to produce iron(II) chloride and hydrogen.
(a)
(b)
(c)
(d)
3.
calcium oxide
lithium nitrate
aluminium hydroxide
magnesium nitrate
Write a balanced equation for this reaction using simple formulae and state
symbols.
Write a balanced ionic equation for this reaction, again showing state symbols.
Name the spectator ion(s) in this reaction.
Re-write the ionic equation omitting the spectator ions.
40 cm3 of 0.2 moll-1 sodium hydroxide solution neutralised 20cm3 of nitric acid, the
balanced equation for the reaction being:
HNO3 + NaOH
⟶
NaNO3 + H2O
Calculate
(a) the number of moles of alkali present
(1)
(2)
(1)
(2)
(b)
(c)
4.
the number of moles of acid reacting
the concentration of the acid.
(3)
A pupil carried out a titration and obtained the following results.
1st titre
2nd titre
0.5
21.7
0.3
21.7
42.4
20.8
21.2
20.7
20.5
Rough titre
Initial
burette
reading/cm3
Final burette
reading /
cm3
Volume used
/ cm3
(a) How would the pupil know when to stop adding acid from the burette?
(b) What average volume should be used to calculate the number of moles of
sulphuric acid needed to neutralise the potassium hydroxide solution?
(c) Calculate the number of moles of sulphuric acid in this average volume.
(d) The equation for the titration reaction is
(1)
(1)
(1)
H2SO4 + 2KOH ⟶ K2SO4 + 2H2O
Calculate the number of moles of potassium hydroxide in 20cm3 of the potassium
hydroxide solution. Show your working clearly.
5.
(1)
A chemical company uses concentrated ammonia. The company selling the ammonia
solution checks its concentration in the following way:


The concentrated ammonia solution is diluted exactly 100 times.
The diluted solution of ammonia is titrated with 0.1 moll-1 hydrochloric acid.
In one check it was found that 20cm3 of the diluted ammonia solution required 25 cm3
of 0.1 moll-1 hydrochloric acid for the neutralisation.
Calculate the concentration of the concentrated ammonia solution, given that the balanced
equation for the neutralisation reaction is:
NH3 + HCl ⟶ NH4Cl
(3)
(20)
Chemical changes and Structure:
Homework 10: Calculations from equations
1.
What mass of water is produced when 160g of methane is burned?
(2)
2.
How much oxygen is required to burn 32g of sulphur to produce sulphur dioxide?
(2)
3.
What mass of carbon dioxide forms when 15g of calcium carbonate reacts
with hydrochloric acid?
(3)
What mass of nitric acid reacts with copper(II)oxide to form 18.8g of
copper(II)nitrate?
(3)
4.
(10)
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