Answers to UNIT 5 Self Test:

1.    (d) Each formula contains 12 oxygen atoms so 10 formula units gives 120 oxygen atoms.

2.    (a) NaCl is ionic and thus is molar mass is called a gram formula mass.

3.    (b) 95.3 g = 24.3g + 2(35.5)

4.    (d) units here cancel to leave grams

5.    (c) this formula contains a whole number that is not the lowest possible.

6.    (b) 2(14)/80 * 100

7.    (c) 66/[12 + 2 + 19] = 66/33 = 2 multiply each subscript in the empirical formula by 2 to get answer.

8.    (e) 2.00 moles * 6.022 x 10²³ molec/mol * 2 atoms/molec = 2.41 x 10²⁴ Cl atoms

9.    (c) the number is the same as the subscript on oxygen in the formula

10.  (d) there are twice as many H atoms than N atoms in the compound

11.  (d) 6 atoms/molec of H in C₂H₆ * 13 molecules = 78 atoms of H

Part 2 Problems

1.    (a) 6.36 g    (b) 147 g     (c) 0.043 g    (d) 5.15 g

2.    (a) 8.36 x 10²³ molecules    (b) 95.2 mL    (c) 8.47 x 10¹² formula units

3.    1.96 g/L        4.    (a) 68.4% Cr; 31.6% O    (b) 31.3% Sn; 68.7% Cl

5.    Na₂S₂O₃        6.  C₃H₆