Download Gen Chem Final--review problems Fall 2006

Gen Chem Final--review problems
Fall 2006
This is a list of questions to help you study for the final exam. You should know that this list is
not all-inclusive. I recommend using this list only in conjunction with going back over the old
practice sheets (still online) and exams.
1.)
What is the molecular formula for potassium phosphate?
2.)
What is the result of 5.771 x (13.01 – 8.116) to the proper number of sig. figs? What is
the answer in scientific notation?
3.)
A substance has a density of 2.94 g/mL. What is the mass of 2.50 L of the substance?
4.)
How many protons, neutrons, and electrons are in 39K+?
5.)
What is the mass of a sample of carbon containing 4.50 x 1025 atoms? How many moles
of carbon are in the sample?
6.)
Determine the mass percent of carbon in CH3COOH.
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7.)
Determine the empirical formula for a compound that was analyzed to contain 71.65%
Cl, 24.27% C, and 4.08% H.
8.)
Name the following compounds and state whether they are ionic or covalent:
a. CaCl2
b. SF6
c. CCl4
d. K3PO4
9.)
Write a balanced chemical equation for the reaction between elemental carbon, hydrogen,
and oxygen to form acetic acid, CH3COOH. What mass of carbon is necessary to
produce 100.0 g of acetic acid?
10.)
In the formation of CH4 from its elements (C and H2), 1.00 g of each element is placed in
the reaction vessel and allowed to react. Identify the limiting reagent and calculate the
mass of CH4 formed.
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11.)
Distinguish the following reactions as oxidation-reduction, precipitation, or acid/base.
a. 2 Sr + O2 Æ 2 SrO
b. H2 + Cl2 Æ 2 HCl
c. HBr + NH3 Æ NH4+ + Br-
d. Ba(NO3)2 + Na2SO4 Æ 2NaNO3 + BaSO4
e. (NH4)2CO3 + CaCl2 Æ CaCO3 + 2 NH4Cl
f. 3 Pt + 4 HNO3 + 18 HCl Î 3 H2PtCl6 + 4 NO + 8 H2O
12.)
13.)
14.)
15.)
For the precipitation reaction/s above in problem 1, please add the appropriate ‘state’ (i.e.
solid or aq) to each species.
For the oxidation/reduction reaction/s above, please identify the species that is being
oxidized and the species being reduced and assign oxidation numbers to each atom.
For the acid/base reaction above in problem 1, identify the Bronsted acid/conjugate base
pair and the Bronsted base/conjugate acid pair.
Which main-group from the periodic table is described by each of the following:
a.)
In water, ionizes to form +2 ions
b.)
All elements of this group exist naturally as diatomic molecules.
c.)
Has both metals and nonmetals. The nonmetals usually form four covalent bonds.
d.)
Known as the alkali metals.
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16.)
What volume of 1.0 M NaOH is needed to prepare 1.00 L of 0.15 M NaOH?
17.)
In a solution calorimeter, 50.0 mL of 0.100 M AgNO3 solution and 50.0 mL of 0.100 M
HCl are mixed. The following reaction occurs:
Ag+(aq) + Cl-(aq) Î AgCl(s)
If the two solutions were initially at 22.6°C and the final temperature is 23.4°C, calculate
qrxn and ΔHrxn. Assume that the surroundings are mostly water and therefore the specific
heat and the density of H2O can be used. S = 4.184 J/g°C and density = 1.00 g/mL.
18.)
Consider the following reaction:
2 Na2O2(s) + 2H2O(l) Î 4 NaOH(s) + O2(g)
ΔHorxn = -126 kJ/mol rxn
a.)
Is the reaction endothermic or exothermic?
b.)
Determine the ΔHf° for Na2O2 given ΔHf° H2O = -285.8 kJ/mol and ΔHf° NaOH
= -426.7 kJ/mol.
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19.)
Calculate ΔH°rxn for the production of nitrogen oxide from N2 and O2,
N2(g) + O2(g) Î 2NO(g)
from the following data.
ΔHo = 33.2 kJ/mol rxn
ΔHo = -57.1 kJ/mol rxn
½ N2(g) + O2(g) Î NO2(g)
NO(g) + ½ O2(g) Î NO2(g)
20.)
Ozone (O3) in the atmosphere can reaction with nitric oxide (NO):
O3(g) + NO(g) → NO2(g) + O2(g).
Calculate the ΔG° for this reaction at 25°C. (ΔH° = -199 kJ/mol, ΔS° = -4.1 J/K·mol)
21.)
Determine the frequency and energy of light having a wavelength of 654.7 nm.
22.)
Give a set of 4 quantum numbers that would correspond to the outermost electron in an
atom of sodium.
23a.) What is the electron configuration for Se (atomic number 34) and Ca+2 ?
23b.) Determine the number of valence electrons for Se.
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23c.) Write the orbital diagram describing the valence electrons in Se.
24.)
Determine the total number of valence electrons in SCN-.
25.)
Rank the following elements in order of increasing atomic size: Si, Al, S, Ar.
26.)
Rank the following elements in order of increasing ionization energy: Sr, Ba, Mg, Ca
27.)
Review of periodic trends. Circle the best response or fill in the blank.
a.)
Electronegativity [increases/decreases] from Li to Cs.
b.)
In the third period, the largest neutral atom is ______________.
c.)
Bromide has a [larger/smaller] radius than a bromine atom.
d.)
Carbon tends to always form [ three / four ] bonds.
e.)
Beryllium is [ larger / smaller ] than barium.
28.)
What is the pressure (in mm Hg) of a gas at 0.98 atm ?
29.)
Determine the final temperature of a gas sample, initially with T = 200 K, if the pressure
is doubled and the volume is halved.
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30.)
At constant V and T, if the number of moles of a gas changes from 0.1 to 0.3, the
pressure will increase/decrease/stay the same by _________-fold
31.)
What is the volume of 64.0 g of O2 at STP?
32.)
What is the density of O2 at STP?
33.)
Determine the total volume of gas produced when 50.0 g of C6H12 is completely
combusted at 110° C and 1.0 atm pressure.
C6H12(l) + 9 O2(g) Î 6 CO2(g) + 6 H2O(g)
34.) For NCl3, PBr5, and SF4 : name the compound, draw a Lewis structure, give the formal
charges on each atom, determine the molecular geometry, bond angles, whether or not the
molecule is polar, and hybridization around the central atom.
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35.)
Draw the possible resonance structures for NO3-. Are the resonance structures
equivalent, if not, which is/are the best?
36.)
Which of the bonds are polar covalent? Si-H, P-H, S-H, and C-H?
37.)
Predict the intermolecular forces present in each of the following compounds
a. NH3
b. PCl3
c. I2
38.)
Rank the following in order of increasing boiling points: F2, H2, HF
39.)
Which would you expect to have a greater solubility in water: HCl or Cl2? Why?
40.)
Calculate the amount of water (in grams) that must be added to 12.00 g NaCl to yield a
solution that is 23.2% by mass.
41.)
Write the equilibrium constant expression, Kc for the following reaction:
P4(s) + 5O2(g) ⇔ P4O10(s)
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42.)
The reaction to produce ammonia is as follows:
N2(g) + 3H2(g) ⇔ 2 NH3(g)
Kc = 4.52 at 450 K
In a given experiment the equilibrium concentration of NH3(g) was found to be 0.109 M
and the equilibrium concentration of N2(g) was found to be 0.124 M. Determine the
equilibrium concentration of H2(g).
43.)
Consider the equilibrium between HI and its elements:
2 HI(g) ⇔ H2(g) + I2(g)
Kc = 1.51 at 500 K
a.)
If 0.770 moles of HI(g) is placed in a 1.00 L flask, what are the concentrations of
all species present at equilibrium?
b.)
If the pressure is doubled at equilibrium, which direction will the reaction proceed
(left, right, or neither).
44.)
At 900 K, a 1.0 L flask is filled with 0.025 mole C(s), 0.44 moles CO2(g), and 0.55 mol
CO(g). Using the following equilibrium information, determine in which direction, if any,
the reaction will proceed.
C(s) + CO2(g) ⇔ 2 CO(g)
45.)
Kc = 0.89 at 900 K
A certain reaction, A(g) ⇔ B(g) has an equilibrium constant, Kc = 680 at 298 K. At 323
K, the value of Kc is 290. Is this reaction exothermic or endothermic? Why?
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46.)
What is the conjugate acid of HAsO42-? What is the conjugate base of HAsO42-?
47.)
Formic acid (HCO2H) has a Ka = 1.9 x 10-4. Write the equilibrium reaction and the
equilibrium constant expression for formic acid in water. Determine the pH of a 0.35 M
solution.
48.)
Arrange the following 1.0 M aqueous solutions in order of increasing pH.
HNO3 Ka = 28, HClO Ka = 2.9 x 10-8, NH3 Kb = 1.8 x 10-5
NaOH
HNO3
HClO
NH3
49.)
A 0.100 M solution of the weak acid HIO has a pH of 5.81. Determine the Ka for the
acid.
50.)
Ammonia has a Kb = 1.8 x 10-5. Write the equilibrium constant reaction and equilibrium
constant expression for ammonia. Identify the conjugate acid of ammonia and determine
its Ka value.
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51.)
What is the pH of a 0.00288 M solution of HNO3?
52.)
HClO has a Ka = 2.8 x 10-8 and HBrO has a pKa of 8.59. Which is the stronger of these
two weak acids?
53.)
What volume of 0.200 M HCl(aq) is needed to neutralize 4.10 g NaOH(s)?
54.)
What is the pH of a solution that is 0.20 M sodium benzoate and 0.50 M benzoic acid (Ka
= 6.4 x 10-5).
55.)
A buffer is prepared by dissolving 0.300 mol HNO2 (Ka = 4.0 x 10-4) and 0.300 mol
NaNO2 in water to make 1.0 L of solution. What is the pH of the buffer solution?
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56.)
57.)
A decomposition reaction was performed in lab. If you began with 500.0 g of Ni(CO)4,
determine the theoretical yield.
Ni(CO)4(g) Î Ni(s) + 4 CO(g)
b.)
If your yield of Ni was 91.4 g, what is your % yield.
c.)
What is your % error?
The following reaction was performed in lab by collecting the H2 gas over water in a
eudiometer tube:
Mg(s) + 2 HCl(aq) Î MgCl2 (aq) + H2 (g)
If you collect 35.7 mL of H2 gas, at atmospheric pressure of 741.2 mm Hg, at 22.5oC
where H2O has a vapor pressure of 20.5 mm Hg, how many moles of H2 did you collect?
58.)
Given a standard curve for CuCl2 with a linear regression of y = 1.08x + 0.0257, what is
the concentration of a sample of CuCl2 with an absorbance of 0.43?
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