Download VII. Stoichiometry I

VII. Stoichiometry I-Review
1) Gram Formula Mass
Directions: Determine the gram formula mass for the following compounds and/or hydrates.
a) NaNO3
b) KCl
c) Hg2(NO3)2
d) N2O5
e) PbCrO4
f) Fe(ClO4)2
g) MgSO4 · 7H2O
h) SiO2 · 8H2O
2) Conversions
Directions: Convert the following (be sure to give your answer with the correct number of significant
figures and units)
a) What is the mass of 2.54 moles of carbon monoxide?
b) What is the mass of 4.34 moles of SiO2?
c) How many moles are in 39 grams of LiF?
d) How many moles are in 576 grams of SO2 gas?
e) How many moles are in 0.50 grams of CaO?
f) Calculate the number of moles in the following:
i) 3.45 x 1023 atoms of neon
ii) 3.02 liters of ammonia
iii) 2.56 molecules of Fe2O3
g) Calculate the number of grams in the following:
i) 2.30 x 1023 molecules of WO3
ii) 1.06 x 1023 atoms of radon
iii) 45.0 liters of xenon
3) Percent Composition
Directions: Determine the percent composition for each of the following.
a) A 2.85 g sample contains 0.82 g magnesium, 0.41 g carbon, and 1.62 g oxygen. Calculate the
percent composition.
b) Calculate the percent composition for Al2(SO4)3.
c) Calculate the percent composition for Sb2S3.
d) Calculate the percent hydration for CaSO4 · 2H2O.
4) Empirical Formula
Directions: Determine the empirical formula for each of the following.
a) 36.5 % sodium, 38.1 % oxygen and 25.4 % sulfur
b) 28.4 % copper and 71.6 % bromine
c) 39.0 % potassium, 12.0 % carbon, 1.01 % hydrogen and 47.9 % oxygen
d) 60.9 % As and 39.1 % S
e) 76.89 % Re and 23.12 % O
f) 55.81 % C, 3.90 % H, 29.43 % F and 10.85 % N
g) Ninhydrin is a compound that reacts with amino acids and proteins to produce a dark-colored
complex. It is used by forensic chemists and detectives to see fingerprints that might otherwise be invisible.
Ninhydrin’s composition is 60.69 % carbon, 3.40 % hydrogen and 35.92 % oxygen. What is the empirical
formula for ninhydrin?
5) Molecular Formula
Directions: Determine the molecular formulas for compounds having the following empirical
formulas and molar masses:
a) C2H4S; experimental molar mass 179
b) C2H4O: experimental molar mass 176
c) C2H2O; experimental molar mass 254
d) A compound contains 30.45 % nitrogen and 69.55 % oxygen. Its molecular mass is 92.02 g. What
is its molecular formula?
e) What is the molecular formula for the compound that contains: 41.39 % carbon, 3.47 % hydrogen
and 55.14 % oxygen. The experimental molar mass is 116.07.
f) A 0.400 g sample of a white powder contains 0.141 g of potassium, 0.115 g of sulfur, and 0.144 g
of oxygen. What is the empirical formula for the compound?
g) A 2.65 g sample of salmon-colored powder contains 0.70 g of chromium, 0.65 g of sulfur, and 1.30
g of oxygen. The molar mass is 392.2. What is the formula of the compound?