This document contains chemistry problems involving calculating percentages of elements in compounds, determining empirical and molecular formulas, and identifying formulas of hydrates. It asks the student to find the percentage of oxygen in several compounds, calculate grams of oxygen in a given amount of compound, determine empirical formulas based on percentage composition, calculate molecular formulas given empirical formulas and molar masses, and write formulas for hydrates when given the masses of the anhydrous compound and water.

1. Chapter 8B Name________________
Mr. Bennett Date__________
1. Find the percentage of oxygen in the following compounds:
a. KMnO4 b. SiO2 c. Mg3(AsO4)2
2. How many grams of oxygen are in 75.75 grams of SiO2?
3. Find the empirical formula if:
a. the compound contains 35.9 % Al and 64.1 % S b. you have 35.6 % P and 64.4% O
c. the cpd is 38.7 % Ca, 20.0 % P, and 41.3 % O d. it is 6.05 % Li, 45.2 % Cr, and 48.7 % O
e. the compound contains 7.88 g of aluminum, 14.06 g of sulfur, and 28.06 g of oxygen.
4. What is the molecular formula of a compound:
a. that has an empirical formula of CH and a mass of 78.1 g/mol ?
b. that has 0.44 g of H, 6.92 g of O and a mass of 34.00 u.

2. c. that contains 85.6 % carbon and 14.36 % hydrogen. Mass = 42.1 g/mol
d. that is 56.38 % P, 43.62 % O, and 219.9 u.
5. 1.996 grams of an oxide contains 0.606 grams of nitrogen and has a mass of 92.0 g/mol,
what is the molecular formula?
6. Find the formula for the following hydrates:
a. 0.391 grams of LiSiF6 and 0.0903 g of H2O
b. 0.737 g of Mg SO3 and 0.763 g of H2O
c. 95.3 g of Li NO3 and 74.7 g of H2O
d. 76.9 % of CaSO3 and 23.1 % H2O
e. 89.2 % BaBr2 and 10.8 % H2O