Sample Mid-term Examination Chemistry 217

Sample Mid-term Examination Chemistry 217
Multiple-choice Questions (2 marks each)
Circle appropriate response.
1. A sky-blue aqueous solution was labeled "chromium(II) perchlorate". This solution
contains the ions
A) Cr2O2+ and ClO4–.
B) Cr2O4+ and Cl–.
C) Cr2+ and Cl–.
D) Cr2+ and ClO4–.
E) Cr3+ and ClO4–.
2.
A)
B)
C)
D)
E)
The name of the compound Hg2Cl2 is
mercury(II) chloride.
mercury(I) chloride.
dimercury dichloride.
mercury dichloride.
dimercury chloride.
3.
A)
B)
C)
D)
E)
What is the charge on the anion in Cr2(SO3)3?
–2
–6
–3
–4
+3
4. What volume of 0.202 M NaCl solution should you transfer so as to have a sample of
solution that contains 0.354 mol NaCl?
A) 1.75 L
B) 5.71 mL
C) 71.5 mL
D) 1.75 mL
E) 0.571 L
5.
A)
B)
C)
D)
E)
The prefix corresponding to the factor 10–9 is
nano.
pico.
micro.
kilo.
milli.
6.
A)
B)
C)
D)
E)
What is the molar mass of sodium hydrogen carbonate?
107.0 g/mol
83.00 g/mol
68.01 g/mol
106.0 g/mol
84.01 g/mol
7.
A)
B)
C)
D)
E)
Which of the following is correct with respect to the reactions of PbO?
PbO does not react with acid or base.
PbO dissolves in water to give hydroxide ions.
PbO reacts with base to give Pb(OH)4–.
PbO reacts with water to give hydrogen gas.
PbO is insoluble in base.
8.
A)
B)
C)
D)
E)
What type of reagent is required to convert HNO2 to NO2–?
base
acid
reducing agent
oxidizing agent
neutralization reagent
9.
A)
B)
C)
D)
E)
Which of the following is soluble in water?
lead(II) sulfate
lead(II) nitrate
lead(II) phosphate
lead(II) chromate
lead(II) bromide
10. How many moles of H+ ions are contained in 375 mL of an aqueous solution which is
0.200 M oxalic acid, H2C2O4(with two acidic protons)?
A) 0.0375 mol
B) 0.300 mol
C) 0.150 mol
D) 0.600 mol
E) 0.0750 mol
11. How many moles of carbon monoxide gas are produced from the reaction of 5.00 moles
of SnO2(s) with 8.00 moles of carbon according to the equation below?
SnO2(s) + 2C(s) ® Sn(s) + 2CO(g)
A) 10.0 mol
B) 16.0 mol
C) 5.00 mol
D) 4.00 mol
E) 8.00 mol
12.
A)
B)
C)
D)
E)
How many mL of 0.200 M HCl(aq) are neutralized by 5.00 g of Mg(OH)2(s)?
21.4 mL
2330 mL
857 mL
429 mL
1710 mL
13. A 20.0-mL sample of sulfuric acid from a lake near a mine was titrated to the
stoichiometric point with 9.92 mL of 0.0120 M NaOH(aq). What is the molarity of
sulfuric acid in the sample?
A) 0.00238 M
B) 0.00398 M
C) 0.00595 M
D) 0.00298 M
E) 0.0119 M
14. Calculate the volume of carbon dioxide produced at STP by the combustion of 227 grams
of propane, C3H8(g).
A) 462 L
B) 0.690 L
C) 0.920 L
D) 116 L
E) 346 L
15. Consider the following reaction.
CS2(g) + 3O2(g) ® CO2(g) + 2SO2(g)
If 2.50 moles of CS2(g) are burned, what volume of SO2(g) is produced at STP?
A) 112 L
B) 56.0 L
C) 5.00 L
D) 22.4 L
E) 28.0 L
16.
A)
B)
C)
D)
E)
Calculate the volume occupied by 12.4 g of nitrogen gas at STP.
4.96 L
10.9 L
22.4 L
19.8 L
9.92 L
17.
A)
B)
C)
D)
E)
Calculate the volume occupied by 5.75 moles of chlorine gas at STP.
258 L
141 L
129 L
64.4 L
22.4 L
18. If the standard enthalpy of formation of N2O(g) is +82.05 kJ · mol–1, calculate the
reaction enthalpy for
2N2O(g) ® 2N2(g) + O2(g)
A) +82.05 kJ
B) –82.05 kJ
C) –41.03 kJ
D) –164.10 kJ
E) +164.10 kJ
19. The standard enthalpies of combustion of CH3OH(l), C(s), and hydrogen gas are –726, –
394, and –286 kJ · mol–1, respectively. What is the standard enthalpy of formation of
CH3OH(l)?
A) –620 kJ · mol–1
B) –240 kJ · mol–1
C) –484 kJ · mol–1
D) +620 kJ · mol–1
E) –240 kJ · mol–1
20. Consider the heating curve for one mole of a substance that melts at –23oC and boils at
327 oC.
A)
B)
C)
D)
E)
If the heat is added at a constant rate of 180 J/min, the molar enthalpy of vaporization of
the substance is
+1.5 kJ · mol–1
+0.24 kJ · mol–1
+0.60 kJ · mol–1
+2.7 · mol–1
+3.0 kJ · mol–1
21. The standard enthalpy of combustion of octane, C8H18(l), is –5471 kJ · mol–1. The
standard enthalpies of formation of H2O(l) and CO2(g) are –285.83 and –393.51 kJ · mol–
1, respectively. What is the standard enthalpy of formation of octane?
A) –689 kJ · mol–1
B) +250 kJ · mol–1
C) –438 kJ · mol–1
D) +689 kJ · mol–1
E) –250 kJ · mol–1
Short-answer Questions (4 marks each)
22. Fill in the blanks and the correct symbol for "E" in the following table.
Symbol = E
E
75E (Z = 33)
E
Atomic Number
24
___
38
Number of Electrons
24
___
38
Number of Neutrons
28
___
49
23. Complete and balance the equations for any reactions which will occur for the following
situations. Write the net ionic equation where appropriate.
a) BaSO4(s) + NaCl(aq) ®
b) Pb(NO3)2(aq) + Na2CrO4(aq) ®
c) Ca(OH)2(aq) + H2SO4(aq) ®
24. If 3.00 moles of sulfur dioxide occupy 4.00 L at 120oC, calculate the pressure using both
the van der Waals and ideal gas equations. The van der Waals constants for sulfur dioxide
are a = 6.87 L2 atm mol–2 and b = 0.0568 L mol–1. Explain the results.
25. If the standard enthalpy of combustion of acetylene, C2H2(g), is –1300 kJ · mol–1, how
many liters of acetylene measured at 25oC and 2.62 atm must be burned to liberate 10.0 ×
106 kJ of heat?
Long-answer Questions (6 marks each)
26. The following elemental analysis was found for artificial sweetener aspartame
(commercially sold as NutraSweetTM):
C, 57.1; H, 6.1; N, 9.5; and O 27.2% by mass
What is the empiracal formula of aspartame?
27. Cobalt(II)chloride exists as a hydrated salt that can be represented by the formula CoCl2 .
xH2O. In an experiment to determine the exact formula of this hydrated salt, 1.024 g of
the hydrate was dissolved in 250 mL of water and excess sodium hydroxide was added to
the resulting solution. The reaction that occured produced 0.573 g of cobalt(II)hydroxide.
Determine the formula of hydrated cobalt(II)hydroxide (i.e. the value of x in CoCl2 .
xH2O)
28. A 2.032 g sample of menthol (C10H20O) is introduced into a bomb calorimeter and
completely burned with oxygen. The heat of combustion was found to be -6310 kJ/mol.
The temperature of the calorimeter increases from 22.37 to 36.52 oC. Calculate the heat
capacity of the calorimeter:
*** END OF EXAMINIATION ***
Mid-term Examination Chemistry 217
Answer Key
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
D
B
A
A
A
E
C
A
B
C
E
C
D
E
A
E
C
D
E
A
E
33, 33, 42
a) BaSO4(s) + NaCl(aq) ® No reaction
b) Pb(NO3)2 (aq) + Na2CrO4 (aq) ® PbCrO4 (s) + 2NaNO3 (aq)
Net: Pb2+ (aq) + CrO42- (aq) ® PbCrO4 (s)
c) Ca(OH)2 (aq) + H2SO4 (aq) ® Ca SO4 (s) + 2H2O (l)
Net: Ca2+ (aq) + SO42- (aq) ® Ca SO4 (s)
24.Ideal gas: 24.2 atm and VDW gas: 21.4 atm
Only at low pressures will VDW gas approximte an ideal gas.
25. 7.2 ´ 104 L
26.
C
H
N
O
(57.1)/(12)
(6.1)/(1)
(9.5)/(14)
(27.2)/(16)
=
=
=
=
(Wt/MWt)
Divide by
.67857
Best
Ratio
4.7583
6.1
.67857
1.70
7.01
8.99
1
2.5
14
18
2
5
C14H18N2O5
27. 0.573 g of Co(OH)2 ===> 6.16 x 10-3 moles
Moles of CoCl2 . xH2O = Moles of Co(OH)2
MWt (CoCl2 . xH2O) = (1.024 g)/(6.16 x 10-3 moles) = 166.2 g/mol
CoCl2 . xH2O = 166.2
xH2O = 36.2
x = 36.2/18 = 2
CoCl2 . 2H2O
28. 2.032 g ==> 1.302 x 10-2 mol menthol
(-6310 kJ/mol)(1.302 x 10-2 mol) = -82.19 kJ
q = -C x DT
-82.19 kJ = -C(36.52 - 22.37 oC)
C = (-82.19 kJ)/(14.15 oC) = 5.81 kJ/oC or 5.81 kJ/K