1.
Arrange the following in order of increasing boiling point: RbCl, CH3Cl, CH3OH,
CH4.
Ans: CH4 < CH3Cl < CH3OH < RbCl
2.
Which one of the following substances should exhibit hydrogen bonding in the liquid
state? SiH4 H2 H2S CH4 CH3NH2
Ans: CH3NH2
3.
Calculate the molality of a solution containing 14.3 g of NaCl in 42.2 g of water.
Ans: 5.80 m
4.
Calculate the approximate freezing point of a solution made from 21.0 g NaCl and
1.00x102 g of H2O. [Kf of water is 1.86°C/m.]
Ans: –13.4°C
5.
A first-order reaction has a rate constant of 3.00x10–3 s–1. The time required for the
reaction to be 75.0% complete is
Ans: 462 s
6.
When the concentrations of reactant molecules are increased, the rate of reaction
increases. Explain why.
Ans: As the reactant concentration increases, the frequency of molecular collisions
increases.
7.
If one starts with pure NO2(g) at a pressure of 0.500 atm, the total pressure inside the
reaction vessel when 2NO2(g)
2NO(g) + O2(g) reaches equilibrium is 0.674
atm. Calculate the equilibrium partial pressure of NO2.
Ans: 0.152 atm
8.
At 340 K, Kp = 69 for the reaction H2(g) + I2(g)
2HI(g). 50.0 g of HI is injected
into an evacuated 5.00-L rigid cylinder at 340 K. What is the total pressure inside the
cylinder when the system comes to equilibrium?
Ans: 2.18 atm
9.
Acid strength decreases in the series HI > HSO4– > HF > HCN. Which of these
anions is the weakest base?
Ans: I–
1
10.
Arrange the acids HOCl, HClO3, and HClO2 in order of increasing acid strength.
Ans: HOCl < HClO2 < HClO3
11.
Which of the following yields a basic solution when dissolved in water?
KNO2
NH4Cl
NaCl SO2
Ans: KNO2
12.
Calculate the concentration of oxalate ion (C2O42–) in a 0.175 M solution of oxalic
acid (C2H2O4). [For oxalic acid, Ka1 = 6.5 x 10–2, Ka2 = 6.1x10–5.]
Ans: 6.1 x 10–5 M
13.
Consider the weak bases below and their Kb values:
C6H7O
C2H5NH2
C5H5N
Kb = 1.3x10–10
Kb = 5.6 x10–4
Kb = 1.7 x10–9
Arrange the conjugate acids of these weak bases in order of increasing acid strength.
Ans:
14.
C2H5NH3+< C5H5NH+ < C6H7OH
When 2.0 x 10–2 mole of nicotinic acid (a monoprotic acid) is dissolved in 350. mL of
water, the pH is 3.05. What is the Ka of nicotinic acid?
Ans: 1.4 x10–5
15.
Calculate the pH of a buffer solution prepared by dissolving 0.20 mole of cyanic acid
(HCNO) and 0.80 mole of sodium cyanate (NaCNO) in enough water to make 1.0
liter of solution.
[Ka(HCNO) = 2.0 x10–4]
Ans: 4.30
16.
Consider a buffer solution prepared from HOCl and NaOCl. Write the net ionic
equation for the reaction that occurs when NaOH is added to this buffer.
Ans: OH–
17.
H2O + OCl–
You have 500.0 mL of a buffer solution containing 0.30 M acetic acid (CH 3COOH)
and 0.20 M sodium acetate (CH3COONa). What will the pH of this solution be after
the addition of 20.0 mL of 1.00 M NaOH solution? [Ka = 1.8 x10–5]
Ans: 4.71
2
18.
Calculate the pH at the equivalence point for the titration of 0.20 M HCl with 0.20 M
NH3 (Kb = 1.8 x 10–5).
Ans: 5.12
19.
The molar solubility of magnesium carbonate is 1.8 x 10–4 mol/L. What is Ksp for this
compound?
Ans: 3.2 x 10–8
20.
Solid sodium iodide is slowly added to a solution that is 0.0050 M Pb2+ and 0.0050 M
Ag+. [Ksp (PbI2) = 1.4 x 10–8; Ksp (AgI) = 8.3 x 10–17] What compound will precipitate
first?
Ans:
21.
AgI
Calculate the minimum concentration of Mg2+ that must be added to 0.10 M NaF in
order to initiate a precipitate of magnesium fluoride. (For MgF2 , Ksp = 6.9x 10–9.)
Ans: 6.9 x 10–7 M
22.
Will a 0.1 M solution of Na2HPO4(aq) be acidic, basic, or neutral? [given that
Ka=4.8x10-13 & Kb=1.6 x 10-7]
Ans: basic
23.
What is the missing symbol in this plutonium fission reaction?
239
94
Pu +
Ans:
24.
0
n  ______ +
97
1
Sr + 3 n
38
0
146
Ba
56
Radium-226 decays by alpha emission. What is its decay product?
Ans:
25.
1
222
Rn
86
Find the nuclear binding enrgy of potassium-40 (atomic mass = 39.9632591 amu) in
units of joules per nucleon. [Data: neutron mass = 1.674928x 10–24 g; proton mass =
1.672623x10–24g; electron mass = 9.109387x 10–28 g; NA = 6.0221367 x 1023 /mol; c
= 2.99792458 x 108 m/s; 1 g = 6.022 x 1023 amu; 1J=1kg/m2.s2]
Ans: 1.33 x 10–12 J/nucleon
26.
A nucleus of carbon-14 lies above the belt of stability. Write an equation for
radioactive decay of carbon-14.
Ans: 146C
14
7N
+ 0-1β
3
27.
A radioactive isotope of Rb-87 decays as follow:
25

25
0
β
t1/2 = 15 hour
1
Starting with 100g of Na-25, calculate the quantity of Mg-25 produced after 19 hours.
Ans: 58.43 g Mg.
28.
11Na
12Mg
+
What is the monomer of natural rubber? Draw its structure and name it?
Ans: Structural formula of isoprene.
2-methylbuta-1,3-diene
29.
CH2ClCH2–OH
+ 2[O] K2Cr2O7 /
H2SO4
Reflux
Ans: CH2ClCOOH
30.
?
+ H2 O
(chloroethanoic acid)
CH2 =CH–CH3 + HBr
?
Ans: CH3 -CHBr–CH3 (2-bromo propane)
31.
H2SO4
Heat
?
+
H 2O
OH
Ans:
32.
(cyclopentene)
Write chemical equations to show the steps involve in the mechanism for the
polymerization of polyethylene, using Benzoyl peroxide radical as the initiator.
Ans: in the lecture note.
4