1. Unit 7 Review Questions Chemistry

2. 1. What is the best definition of atomic mass? A.The average mass of an isotope of an element B.Average mass of all the naturally occurring isotopes of an element C.The mass of the subatomic particles in the nucleus of an element D.The mass of the protons, neutrons and electrons of an element

3. 2. Iodine is 80% 127 I, 17% 126 I, and 3% 128 I. Calculate the average atomic mass of iodine. A.127 amu B.33.3 amu C.126.86 amu D.128 amu

4. 3. What is the molar mass of Yttrium? A.88.9 g/mol B.39 g/mol C.89 g/mol D.128 g/mol

5. 4. What is the molar mass of CaCl 2 ? A.54 g/mol B.111.0 g/mol C.75.5 g/mol D.100 g/mol

6. 5. How many moles are in 2.5 g of CO 2 ? A.3.4 x 10 22 mol CO 2 B.6.6 x 10 25 mol CO 2 C.110 mol CO 2 D.0.057 mol CO 2

7. 6. What is the mass of 3.75 moles of H 2 ? A.1.86 g H 2 B.7.58 g H 2 C.1.12 x 10 24 g H 2 D.4.56 x 10 -22 g H 2

8. 7. How many moles are in 212 L of gas at STP? A.9.46 mol gas B.4,750 mol gas C.5.70 x 10 24 mol gas D.1.57 x 10 -23 mol gas

9. 8. How many moles are in 3.5 x 10 24 atoms of He? A.2.1 x 10 48 mol He B.5.8 mol He C.1.4 mol He D.22 mol He

10. 9. What is the mass of 0.500 L water vapor @STP? A.202 g H 2 O B.0.622 g H 2 O C.0.402 g H 2 O D.0.00124 g H 2 O

11. 10. What is the mass of 15.00 mL of ethanol with density = 0.789 g/mL? A.19.0 g ethanol B.0.0526 g ethanol C.15.8 g ethanol D.11.8 g ethanol

12. 11. What is the density of nitrogen gas @STP? (Hint: you know the molar mass and molar volume.) A.1.25 g/L B.0.625 g/L C.627 g/L D.0.800 g/L

13. 12. What is the molar mass of a gas with a density of 0.003165 g/cm 3 @STP? A.7.08 g/mol B.0.141 g/mol C.70.9 g/mol D.0.0709 g/mol

14. 13. What is the percent composition of chlorine in lead(IV) chloride? A.59.4% Cl B.40.6% Cl C.4.10% Cl D.14.6% Cl

15. 14. What is the empirical formula of a compound that is 32.37% Na, 22.53% S, and 45.05% O? A.NaSO B.Na 2 SO C.Na 2 SO 3 D.Na 2 SO 4

16. 15. What is the molecular formula of a compound that is 40.0% C, 6.72% H, 53.3% O with a molar mass of 180.15 g/mol? A.CHO B.C 6 H 6 O 6 C.CH 2 O D.C 6 H 12 O 6