1. Key: Compound Calculations and Compound Stoichiometry

2. KNO 3 K --> 1 x 39.10 = 39.10 N --> 1 x 14.01 = 14.01 O --> 3 x 16.00 = 48.00 101.11 amu MgCl 2 Mg --> 1 x 24.31 = 24.31 Cl --> 2 x 35.45 = 70.90 95.21 amu

3. Na 2 SO 3 Na --> 2 x 22.99 = 45.98 S --> 1 x 32.06 = 32.06 O --> 3 x 16.00 = 48.00 126.04 amu (NH 4 ) 3 PO 4 N --> 3 x 14.01 = 42.03 H --> 12 x 1.01 = 12.12 P --> 1 x 30.97 = 30.97 O --> 4 x 16.00 = 64.00 149.12 amu

4. CH 3 OH C --> 1 x 12.01 = 12.01 H --> 4 x 1.01 = 4.04 O --> 1 x 16.00 = 16.00 32.05 amu NaClO Na --> 1 x 22.99 = 22.99 (22.99/74.44)100 = 30.9 Cl --> 1 x 35.45 = 35.45 (35.45/74.44)100 = 47.6 O --> 1 x 16.00 = 16.00 (16.00/74.44)100 = 21.5 74.44 grams

5. Copper II sulfate CuSO 4 Cu --> 1 x 63.55 = 63.55 (63.55/159.61)100 = 39.8 S --> 1 x 32.06 = 32.06 (32.06/159.61)100 = 20.1 O --> 4 x 16.00 = 64.00 (64.00/159.61)100 = 40.1 159.61 grams Aluminum oxide Al 2 O 3 Al --> 2 x 26.98 = 53.96 (53.96/101.96)100 = 52.9 O --> 3 x 16.00 = 48.00 (48.00/101.96)100 = 47.1 101.96 grams

6. SiO 2 Si --> 1 x 28.09 = 28.09 (28.09/60.09)100 = 46.7 O --> 2 x 16.00 = 32.00 (32.00/60.09)100 = 53.3 60.09 grams Ammonium sulfate (NH 4 ) 2 SO 4 N --> 2 x 14.01 = 28.02 (28.02/132.16)100 = 21.2 H --> 8 x 1.01 = 8.08 (8.08/132.16)100 = 6.1 S --> 1 x 32.06 = 32.06 (32.06/132.16)100 = 24.3 O --> 4 x 64.00 = 64.00 (64.00/132.16)100 = 48.4 132.16 grams

7. Ammonium phosphate (NH 4 ) 3 PO 4 N --> 3 x 14.01 = 42.03 (42.03/149.12)100 = 28.2 H --> 12 x 1.01 = 12.12 (12.12/149.12)100 = 8.1 P --> 1 x 30.97 = 30.97 (30.97/149.12)100 = 20.8 O --> 4 x 16.00 = 64.00 (64.00/149.12)100 = 42.9 149.12 grams

8. Element%=gramsMoles (divide by molar mass) Smallest Ratio (divide by smallest mole) Compound’s Chemical Formula Fe 63.52 63.52/55.85 = 1.1371.137/1.137 = 1 FeS S 36.48 36.48/32.06 = 1.1381.138/1.137 = 1 K 31.9 31.9/39.10 =.816.816/.815 = 1 KClO 3 Cl 28.9 28.9/35.45 =.815.815/.815 = 1 O 39.2 39.2/16.00 = 2.452.45/.815 = 3 F 259.2 259.2/19.00 = 13.6413.64/3.40 = 4 F 4 C C 40.8 40.8/12.01 = 3.403.40/3.40 = 1

9. Element % = gramsMoles (divide by molar mass) Smallest ratio (divide by smallest moles) Compound’s Chemical Formula Cd78.0 78.0/112.41 =.694.694/.686 = 1 CdS S22.0 22.0/32.06 =.686.686/.686 = 1 Al32 32/26.98 = 1.21.2/1.2 = 1 AlF 3 F68 68/19.00 = 3.63.6/1.2 = 3 Ca33.36 33.36/40.08 =.8323.8323/.8323 = 1 CaSO 3 S26.69 26.69/32.06 =.8325.8325/.8323 = 1 O40.00 40.00/16.00 = 2.52.5/.8323 = 3 Ag87 87/107.87 =.81.81/.41 = 2 Ag 2 S S13 13/32.06 =.41.41/.41 = 1

10. 18. n = 52.08/13.02 = 4 4(CH) = C 4 H 4 19. n = 60.06/30.03 = 2 2(CH 2 O) = C 2 H 4 O 2 20. n = 283.89/141.97 = 2 2(PO 2 ) = P 2 O 4 21. n = 232.41/77.47 = 3 3(OCNCl) = O 3 C 3 N 3 Cl 3 22. B 78.3/10.81 = 7.24 7.24/7.24 = 1 H 21.7/1.01 = 21.5 21.5/7.24 = 3 BH 3 n = 27.67/13.84 = 2 2(BH 3 ) = B 2 H 6

11. 2) 2.5 moles O 2 = ? molecules 2.5 moles O 2 x (6.02x10^23) molecules = 1.5x10^24 molecules 1 1 mole 4) 0.0024 moles C 13 H 18 O 2 = ? molecules 0.0024 moles C 13 H 18 O 2 x (6.02x10^23) molecules = 1.4x10^21 molecules 1 1 mole 4) 500 mg  0.5 g C 13 H 18 O 2 = ? molecules 0.5 g C 13 H 18 O 2 x (6.02x10^23) molecules = 1.4x10^21 molecules 1 206.31 g

12. 6) 47.5 g C 3 H 8 O 3 = ? molecules 47.5 g C 3 H 8 O 3 x (6.02x10^23) molecules = 3.10x10^23 molecules 1 92.11 g 8) 9.3541x10^13 particles = ? moles 9.3541x10^13 particles x _____1 mole____ = 1.5538x10^-10 mole 1 (6.02x10^23 particles) 10) 3.12 mol MgCl 2 = ? grams 3.12 mol MgCl 2 x 95.21 grams = 297 grams 1 1 mole