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Coppin State CollegeDepartment of Natural Sciences

CHEM 103.101 Exam #3Dr. Alfred N. Amah

Name ______

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This examination consists of two parts: Part A (30 points) consists of 6 multiple choice questions; carefully read each question and all the possible responses. Choose the correct answer by cycling the alphabet before your choice. Part B (70 points) contains (9) short structured questions. Carefully read each question and provide the response.GOOD LUCK!

Part A (30 points). Multiple Choice Questions.

1. The molarity [M] of a solution prepared by dissolving 49.0 g of sulfuric acid H2SO4 ( MW = 98.0 g/mole) in 1000 mL of solution is ?

a. 0.5 M

b. 0.0005 M

c. 5.000 M

d. 1.000 M

2. The number of grams of sulfuric acid in 250 mL of 0.100 M H2SO4 is ? [ Hint: molarity = moles of solute/Liter of solution ; or M = n/L and n = g/MW]

a. 25.5 g

b. 2.45 g

c. 24.5 g

d. 9.8 g

3. How many moles of oxygen are required to combine with 0.500 mol of hydrogen in the reaction that produces water by the following balanced equation?

a. 1.0 mol

b. 0.50 mol

c. 2.0 mol

d. 0.250 mol

4. A student was asked to prepare 12.5 g of NaCl. How many moles is this? [NaCl = 58.5 g/mol]

a.12.5 mol

b. 0.214 mol

c.2.14 mol

d. 5.85 mol

5. What will be the coefficient of O2 when the following incomplete equation is correctly balanced?

a. 2

b. 3

c. 4

d. 6.

6. What will be the coefficient of aluminum (Al) when the following incomplete equation is correctly balanced?

a. 2

b. 3

c. 4

d. 6

Part II.(70 points). Short structured questions. Please answer each of the following questions. Show your work or calculation for each question for proper credit.

7. Formaldehyde, CH2O is a toxic gas with a pungent odor. Large quantities are consumed in the manufacture of plastics, and a water solution of the compound is used to preserve biological specimen. Calculate the mass percentage of each element in formaldehyde. Give your answer to three significant figures. [ C = 12.0; H = 1.0; O = 16.0].(10 credits)

8. Malic acid, an organic acid found in apples, contains C, H, and O in the following ratios: C1.0H1.5O1.25. What is the empirical formula of malic acid? Show all your work for proper credit.(3 credits)

Balance the following chemical equations:

9. When glucose undergoes complete combustion, the products are carbon dioxide and water according to the following chemical equation: ( 10 credits)

______C6H12O6 + _____O2 ______CO2 +______H2O

10. Ammonia reacts with fluorine in the gaseous state to produce dinitrogen tetrafluoride and hydrogen fluoride according to the following equation: (7 Credits)

______NH3(g) + _____F2(g) ______N2F4(g) +______HF(g)

11. (5 credits)

_____KClO3 + _____O2 ______KCl +. ______O2

12. Mandelic acid is an organic acid composed of carbon (63.15%), hydrogen (5.30%), and oxygen (31.55%). Its molar mass is 152.14 g/mol. Determine the empirical and molecular formulas of the acid. [ C= 12.0; H = 1.0; O = 16.00]. (5 credits) Show all work for proper credit.

13. According to balanced chemical equation given below, if 32.0 grams of oxygen and 10.0 grams of hydrogen are mixed. Calculate the maximum grams of water that can be produced.( 10 points)

14. According to the balanced chemical equation given below:

NH4Cl(s)NH3(g) + HCl(g)

If 1.00 gram of NH4Cl(s) ( molar mass is 53.49 g) decompoces and a 75% yield of ammonia (NH3(g) molar mass is 17.03 g ) is obtained, calculate the mass in grams of ammonia in the space provided. (10 points)

15. 2Na(s) + Br2 (l)2NaBr (s)

If 2.3 g of sodium reacts completely, calculate the grams of bromine that will be consumed. (Br = 79.90; Na = 22.99) Show your work in the space provided. (10 points)