Chemistry 3

Concepts of Chemistry

Name______________________ exam 3 Apr. 28, 2020 Total 100 points

5 point each of following questions

1. Consider the general equation.

2A + 3B -------> 2C + D

How many moles of C are produced from 2 mole of A?

A. 1 B. 2 C. 3 D. 4

E. None of the above

2. Consider the general equation.

3A + B -----> 2C

If 1.5g of A reacts with 1.65g of B, what is the mass of C?

A. 1.5g B. 1.65g C. 3.15g D. 3g E. 3.3g

3. How many moles of propane gas, C​3H8, react to produce 6 mole of CO2?

C3H8 (g) + O2(g) --------> CO2(g) + H2O(g)

A. 1 B. 2 C. 3 D. 4 E. None of the above

Hint: Balance the equation first.

4. How many grams of zinc must be reacting to give 8.1 g of ZnO?

2 Zn + O​2(g) --------> 2 ZnO (s)

A. 13g B. 6.5g C. 3.2g D. 6.4g

E. None of these

5. What is the mass (g) of Zn metal needed to react with H2SO4 to produce 44.8L of hydrogen gas at STP?

Zn + H2SO4(aq) --------> ZnSO4(aq) + H2(g)

A. 65g B. 130g C. 260g D. 32.5g

E. None of these

6. If 5 mole of hydrogen gas and 1.5 mole of oxygen gas react, which of the following statement is true based on the balanced chemical equation : 2H2 + O2-------> 2 H2O

A. Oxygen gas is a limiting reactant and 1.5 mole of water will be produced.

B. Oxygen gas is a limiting reactant and 3.0 mole of water will be produced.

C. Hydrogen gas is a limiting reactant and 5.0 mole of water will be produced.

D. Hydrogen gas is a limiting reactant and 10.0 mole of water will be produced.

E. None of these

____7. Which of the following is not an observed property of gases?

A. Gases vary in shape and volume.

B. Gases expand infinitely.

C. Gases compress infinitely.

D. Gases have low density.

E. Gases mix completely.

8. Which of the following express standard atmospheric pressure?

A. 760 mm Hg B. 760 Torr C. 29.9 in Hg

D. 14.7 psi E. all of the above

9. Which of the following mole number is correct for 2.50 L of hydrogen at 100oC and 3.00 atm (given R = 0.0821 atom L /mole K)?

A. 0.914 mole B. 2.50 mole C. 7.50 mole D. 0.245 mole

E. None of the above

_____10. (10 points) Calculate mole number of 2.50 x1023 molecules of CO2.

11. (10 points) Calculate the molar mass of Fe3(PO4)2?(Show your work)

12. (10 points) Calculate the mass in gram, 5.05 x 1021 formula units of BaCl2

13. (10 points) What is the volume of 1.20 x 1022 molecules of ozone gas at STP?

14. (15 points) In an experiment, 2.410g of Copper oxide produced from 1.925g of copper metal heating with oxygen gas. What is the empirical formula of copper oxide?

Hint: solve X, and Y. Find ratio in whole numbers.

Cu + O2 ----------- CuxOy

15. (10 bonus points) Dioxane’s molar mass is 88g/mole. And the percent composition is 54.5% C, 9.15% H, and 36.3% of O. What is the molecular formula for dioxane?