Key: Compound Calculations and Compound Stoichiometry

• KNO3

• K --> 1 x 39.10 = 39.10• N --> 1 x 14.01 = 14.01• O --> 3 x 16.00 = 48.00• 101.11 amu

• MgCl2

• Mg --> 1 x 24.31 = 24.31• Cl --> 2 x 35.45 = 70.90 • 95.21 amu

• Na2SO3

• Na --> 2 x 22.99 = 45.98• S --> 1 x 32.06 = 32.06• O --> 3 x 16.00 = 48.00• 126.04 amu

• (NH4)3PO4

• 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

• CH3OH• 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

• Copper II sulfate CuSO4

• 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 Al2O3

• 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

• SiO2

• 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 (NH4)2SO4

• 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

• Ammonium phosphate (NH4)3PO4

• 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

Element %=grams Moles

(divide by molar mass)

Smallest Ratio(divide by smallest mole)

Compound’s Chemical Formula

Fe 63.52 63.52/55.85 = 1.137 1.137/1.137 = 1 FeSS 36.48 36.48/32.06 = 1.138 1.138/1.137 = 1

K 31.9 31.9/39.10 = .816 .816/.815 = 1

KClO3Cl 28.9 28.9/35.45 = .815 .815/.815 = 1

O 39.2 39.2/16.00 = 2.45 2.45/.815 = 3

F 259.2 259.2/19.00 = 13.64 13.64/3.40 = 4 F4CC 40.8 40.8/12.01 = 3.40 3.40/3.40 = 1

Element % = grams Moles

(divide by molar mass)

Smallest ratio (divide by smallest moles)

Compound’s Chemical Formula

Cd 78.0 78.0/112.41 = .694 .694/.686 = 1 CdSS 22.0 22.0/32.06 = .686 .686/.686 = 1

Al 32 32/26.98 = 1.2 1.2/1.2 = 1 AlF3F 68 68/19.00 = 3.6 3.6/1.2 = 3

Ca 33.36 33.36/40.08 = .8323 .8323/.8323 = 1 CaSO3S 26.69 26.69/32.06 = .8325 .8325/.8323 = 1

O 40.00 40.00/16.00 = 2.5 2.5/.8323 = 3

Ag 87 87/107.87 = .81 .81/.41 = 2 Ag2SS 13 13/32.06 = .41 .41/.41 = 1

18. n = 52.08/13.02 = 4 4(CH) = C4H4

19. n = 60.06/30.03 = 2 2(CH2O) = C2H4O2

20. n = 283.89/141.97 = 2 2(PO2) = P2O4

21. n = 232.41/77.47 = 3 3(OCNCl) = O3C3N3Cl3

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 BH3

n = 27.67/13.84 = 2 2(BH3) = B2H6

• 2) 2.5 moles O2 = ? molecules

• 2.5 moles O2 x (6.02x10^23) molecules = 1.5x10^24 molecules• 1 1 mole

• 4) 0.0024 moles C13H18O2 = ? molecules 0.0024 moles C13H18O2 x (6.02x10^23) molecules = 1.4x10^21 molecules

1 1 mole

• 4) 500 mg 0.5 g C13H18O2 = ? molecules • 0.5 g C13H18O2 x (6.02x10^23) molecules = 1.4x10^21 molecules• 1 206.31 g

• 6) 47.5 g C3H8O3 = ? molecules• 47.5 g C3H8O3 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 MgCl2 = ? grams• 3.12 mol MgCl2 x 95.21 grams = 297 grams• 1 1 mole