Download Exam 2 Review - Iowa State University

Exam 2 Review
Supplemental Instruction
Iowa State University
Ch 3+4
1. Circle the weak electrolytes: LiCl
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Kia
CHEM 177
Kingston
October 3rd, 2016
NH3 HBr Ba(OH)2
CH3COOH H2O
2. Draw what happens when NaCl dissociates in water.
3. How many K+ ions are there in 200.0 mL of a 0.20 M K2SO4 solution?
4. What is the oxidation state of the sulfur atom in the metabisulfite ion S2O5 2–
5. What is the oxidation number of phosphorus atom in sodium dihydrogen phosphate,
NaH2PO4?
6. Write the molecular, total ionic, and net ionic equation for each of the following
reactions:
a. Pb(NO3)2(aq) + KBr(aq) 
b. HBr(aq) + NaHCO3(aq) 
c. Acetic acid is neutralized by barium hydroxide
7. What is the molarity of a NaOH solution if 28.2 mL of a 0.355 M H2SO4 solution is
required to neutralize a 25.0 mL sample of the NaOH solution?
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8. Menthol, the substance we can smell in mentholated cough drops, is composed of C, H,
and O. A 0.1005 g sample of menthol is combusted, producing 0.2829 g of CO2 and
0.1159 g of H2O. If menthol has a molar mass of 156 g/mol, what is the empirical and
molecular formula for menthol?
9. What is the percent yield of C2H2(g) when 50.0 g of CaC2 (molar mass = 64.01 g) reacts
with an excess of water to yield 13.5 g C2H2 (molar mass = 26.04 g) according to the
following reaction:
CaC2(g) +2 H2O(l)  Ca(OH)2(s) + C2H2(g)
10. Which of the following are redox reactions? If it is a redox, indicate which is oxidized
and which is reduced. Indicate the reducing and oxidizing agents as well.
a. 3Fe(NO3)2(aq) + 2Al(s)  3Fe(s) + 2Al(NO3)3(aq)
b. PbS(s) + 4H2O2(aq)  PbSO4(s) + 4H2O(l)
11. What is the molarity of a solution of H3PO4 if 50.00 mL of it is titrated (reacted) with
25.86 mL of 0.1201 M NaOH? Assume that all three hydrogens in H3PO4 react with
NaOH.
12. Answer the following questions using the reaction
2 Na(s) + 2 H2O(l)  2 NaOH(aq) + H2(g)
a. If 1.0 mol Na and 1.0 mol of H2O react and the yield is 85.0%, is there a limiting
reactant? Does the reaction go to completion?
b. If 4.0 mol Na reacts with 6 mol H2O, what is the limiting reactant and how many
moles of the other reactant remain?
c. If you have 5.0 g Na and 10.0 H2O, how many grams of excess reactant do you have?
13. Combustion analysis of toluene, a common organic solvent, gives 5.86 g of CO2, and
1.37g of H2O. If the compound contains only carbon and hydrogen; its molecular weight
is 184 amu. Give its empirical and molecular formulas?
14. Suppose you mix 70 mL of .80M solution of Lead (II) Nitrate with 30 mL of .20 M
Sodium Sulfide. Write the balanced equation. State the limiting reagent(s). How much
precipitate forms? What is the molarity of the non-precipitate product?
Ch 5
15. Know your equations! Write out the equations for internal energy, work, and calorimetry.
16. For the following processes, calculate the change in internal energy of the system and
determine whether the process is endothermic or exothermic.
a. A balloon is cooled by removing 0.655 kJ of heat. It shrinks on cooling, and the
atmosphere does 382 J of work on the balloon.
b. A 100.0 g bar of gold is heated from 25 deg. C to 50 deg. C during which it
absorbs 322 J of heat. Assume the volume of the gold bar remains constant.
17. A gas is confined to a cylinder under constant atmospheric pressure. When the gas
undergoes a particular chemical reaction, it absorbs 824 J of heat from its surroundings
and has 0.65 kJ of PV work done on it by its surroundings. What are the values of deltaH
and deltaE for this process?
18. When solutions containing silver ions and chloride ions are mixed, silver chloride
precipitates:
Ag+ (aq) + Cl- (aq)  AgCl(s)
deltaH= -65.5 kJ
c. Calculate deltaH for the production of 0.450 mol of AgCl by this reaction.
d. Calculate deltaH for the production of 9.00 g of AgCl
e. Calculate deltaH when 9.25x10^-4 mol of AgCl dissolves in water.
19. The specific heat capacity of liquid mercury is 0.14 J/g*K. How many joules of heat are
needed to raise the temperature of 5.00 g of mercury from 15.0 to 36.5 deg. C?