Exam 1 Chem 111, Section 2 (Martin, 1:25pm) Spring 1998

1a. You can identify a pure element from a measurement of its density. An unknown piece of metal, with a mass of 29.454 g, is 2.00 cm long, 2.00 cm wide, and 0.825 cm thick. Which of the following is the element?

(a•) Nickel, 8.91 g/cm3 (b) Titanium, 4.50 g/cm3

(c) Zinc, 7.14 g/cm3 (d) Aluminum, 2.70 g/cm3 (e) Lead, 11.34 g/cm3

2a. Which atom below contains exactly 16 protons?

(a) C (b) O (c•) S (d) Mg (e) N

3a. How many neutrons are in the nucleus of the isotope 33S?

(a•) 17 (b) 18 (c) 19 (d) 20 (e) 33

4a. How many electrons surround the nucleus of the isotope 33S?

(a) 15 (b•) 16 (c) 17 (d) 19 (e) 33

5a. The molar mass of HNO3 is:

(a) 24.0 (b•) 63.0 (c) 47.0 (d) 32.0 (e) 85.0

6a. Which of the following is not a valid (stable) ionic compound?

(a) Mg(OH)2 (b) MgCl2 (c) BeO (d•) Ca2S (e) LiCl

7a. In the ionic compound Fe(OH)2, the Fe has a charge (oxidation number) of:

(a) -2 (b•) +2 (c) 0 (d) -3 (e) +3

8a. Although many of the transition metal cations prefer charges of +2 or +3, other charges are sometimes observed. In the ionic compound NaMnO3, the Mn has a formal charge (oxidation number) of:

(a) +4 (b•) +5 (c) +6 (d) +7 (e) +8

9a. Aspirin has the chemical formula C9H8O4. What is the molecular weight of aspirin?

(a) 100.0 (b) 192.1 (c) 42.0 (d•) 180.2 (e) 94.0

10a. An Alka-Seltzer tablet contains 324 mg of aspirin (C9H8O4), 1904 mg of NaHCO3, and 1000 mg of citric acid (C6H8O7). How many moles of aspirin are in an Alka-Seltzer tablet?

(a) 1.8 (b) 1.8 x 103 (c•) 1.8 x 10-3 (d) 1.1 x 1021 (e) 1.1 x 10-21

11a. The total mass of an Alka-Seltzer tablet is 5.0 g. What is the percent (by weight) of aspirin in an Alka-Seltzer tablet?

(a) 0.065% (b•) 6.5% (c) 38% (d) 0.38% (e) 20%

12a. An unknown amino acid is found to contain 54.94% C, 9.981% H, 24.40% O, and 10.68% N. What is the empirical formula for this amino acid?

(a•) C6H13O2N (b) C5H9O2N (c) C5H11O2N (d) C4H9O2N (e) C6H9O2N

13a. The fatty acid palmitoleic acid (formula C16H30O2) is an energy storage molecule in cells. When energy is required, the fatty acid can be oxidized with a release of energy. For the balanced equation describing the complete oxidation (combustion) of this fatty acid to CO2, what is the coefficient of stoichiometry for O2?

(a) 2 (b) 51 (c) 1 (d) 49 (e•) 45

14a. What is the properly rounded average of the following three masses: 7.899 g, 4.567 g, and 0.46 g?

(a) 4. g (b) 4.3 g (c•) 4.31 g (d) 4.309 g (e) 4.3087

15a. Elemental gold (Au) is dissolved from rock by treating the rock with sodium cyanide (NaCN, a potent respiratory poison•) in the presence of O2.

4 Au (s) + 8 NaCN (aq) + O2 (g) + 2H2O (l) Æ 4 NaAu(CN)2 (aq) + 4 NaOH (aq)

What is the oxidant in this reaction?

(a) H2O (b•) O2 (c) Na+ (d) CN- (e) Au

16a. If you mix aqueous solutions of Pb(CH3CO2)2 and BaCl2, a compound which precipitates from solution contains what element?

(a) C (b) Ba (c•) Pb (d) O (e) nothing precipitates

17a. In the following reaction, which species is the acid?

NH3 (g) + H2CO3 (l) Æ NH4HCO3

(a) H2O (b) NH3 (c•) H2CO3 (d) NH4HCO3 (e) none of these

18a. Which of the following is an oxidation-reduction reaction?

(a) CdCl2 + Na2S Æ CdS + 2 NaCl

(b) Ca(OH)2 + 2HCl Æ CaCl2 + 2 H2O

(c•) Zn + NaNO3 + 2 HCl Æ ZnCl2 + NaNO2 + H2O

(d) Zn(OH)2 + H2SO4 Æ ZnSO4 + 2 H2O

(e) HNO3 + CoCO3 Æ Co(NO3)2 + H2O + CO2

19a. Balance the equation for the following precipitation reaction:

Zn (s) + HCl (aq) Æ H2 (g) + ZnCl2 (aq)

and then write the net ionic equation. Which of the following does not occur in your net ionic equation (ignore stoichiometry)?

(a) Zn2+ (b) H2 (c) H+ (d•) Cl- (e) Zn

20a. Balance the equation for the following precipitation reaction:

CdCl2 + NaOH Æ Cd(OH)2 + NaCl

and then write the net ionic equation. Which of the following does occur in your net ionic equation (be careful of stoichiometry)?

(a) Na+ (b) 2 Na+ (c) OH- (d•) 2 OH- (e) 2 Cl-