CHEM 16 PS

NAME:

I. SIGNIFICANT FIGURES
Determine the correct number of sig fig
1. 0.0001002300
2. 3,039,401,000
3. 6.00
4. 8.0003
5. 6,793
6. 3.040 x 103
7. 400.00
8. 0.000000000890
9. 10,600
10. 0.5009
Express the answer for the given mathematical operation in correct sig fig
11. log(8.9790 x 1021)
12. antilog(0.1)
13. 0.34589 + 0.30
14. (1.310 x 102) x 0.350
15. 0.040500 / 0.030

II. REDOX REACTIONS
Balance the following redox reactions and indicate which chemical species is the oxidizing agent and the reducing agent

ACIDIC CONDITION
1. BrO3- + N2H4 → Br- + N2
2. UO2+ + NO3- → UO22+ + NO(g)
3. S2O42- → S2O32- + HSO3-
BASIC CONDITION
1. Ag(s) + CrO42- → Ag+ + Cr(OH)3 (s)
2. ClO2 → ClO3- + Cl-
3. CH3CH2OH + MnO4- → CH3COO- + MnO2 (s)
What is the oxidation number of the indicated element in each of the following?
a. S in S8
b. Hg in Hg2Cl2
c. Cr in Cr2O72-
d. C in H2C2O4
e. Bi in BiO3-
f. Cl in Cl2O
g. B in B2Br4
h. S in SF6

III. PROBLEM SOLVING
Show full calculation and box the final answer. Express final answer in correct sig fig.

1. How many grams of O atoms are in 580 µL of phosphoric acid (density = 1.885 g/mL)?
2. How many grams of CO2 are produced in the combustion of 2.0 g of lactic acid, CH3CHOHCOOH, in an excess of O2?
3. 31.5 g of Na2S2O3 was made to react with 18.6 g of Cl2 according to the balanced chemical reaction below:
Na2S2O3(aq) + 4Cl2(g) + 5H2O(aq) → 2NaHSO4(aq) + 8HCl(aq)

a. Which is the limiting reactant?
b. What mass (in g) of the excess reactant remains after the reaction?
c. What is the theoretical yield (in g) of NaHSO4?

IV. FINAL BOSS!

A 25.00 g sample of deep-sea sediment was collected and it was found that 12.56% of it was equivalent to the weight (in g) of pure, solid S8. The S8 in the sample was then treated with 150.0 mL of 1.210M HNO3 to produce aqueous SO32- and gaseous NO.

1. What is the balanced redox reaction?
2. Which compound is the oxidizing agent? The reducing agent?
3. Which compound is the limiting reactant?
4. What mass (in g) of the excess reactant remains after the reaction?
5. What mass (in g) of NO is produced in the reaction?
6. How many 36S atoms (%abundance= 0.02000%) are in S8?
7. What is the total number of ions produced in the reaction?
8. What is the %yield of NO if the actual yield is 1.23g?
9. If the sediment was fully dissolved in HNO3, what is the molarity of S8 in the initial solution?
10. Draw the Lewis structures and write the systematic molecular names of the following:
a. HNO3
b. SO32-
c. NO