Problem set 4
Chemical Composition and Stoichiometry
1. A compound was analyzed and was found to contain the following percentages of elements
by mass: carbon, 40.00%; oxygen, 53.28%; hydrogen, 6.72%. Determine the empirical
formula of the compound:
2. A compound contains the following percentages of elements by mass : 48.38% carbon
43.50% oxygen and 8.12% hydrogen. The molar mass of this compound is known to be
~222.25 g/mol. What is its empirical and molecular formula?
3. Calculate the number of molecules for part (a) and (b). Calculate the number of moles for
(c) and (d).
a) 4.86 moles H2SO4
b) 0.994 mole of C6H12O6
c) 6.811 g Ca(NO3)2
d) 8.11×1081 molecules CO2
Dr. Behrang Madani
Chemistry 100
IVC
4. Calculate the percent by mass of each element in Al(NO2)3 and C8H6O4.
5. How many moles of hydrogen are needed to completely react with 12 grams of nitrogen?
N2 + 3H2  2NH3
6. How many grams of ammonia gas is produced if 1.39g of ammonium chloride reacts
completely?
NH4Cl + NaOH  NH3 + NaCl + H2O
7. How many molecules of CO2 gas is produced if 53.1g of Na2CO3 is formed?
2NaHCO3  Na2CO3 + H2O + CO2
8. In the following reaction, 2.3 mole of CN2H4O is produced. Find the volume of CO2 gas in
liter that has been used:
2NH3(g) + CO2(g)  CN2H4O + H2O
Dr. Behrang Madani
Chemistry 100
IVC