# Worksheet 1C: Percent Mass, Moles, and Avogadros Number


## 1. Calculate each of the following quantities

1. Mass in grams of 0.523 moles of $$KCl$$
2. Moles of Oxygen atoms in 12.7 g of $$Ba(NO_3)_2$$
3. Number of nitrogen atoms in 92.6 g of $$NH_4NO_2$$
4. Mass of $$2.04 \times 10^{21}$$ molecules of dinitrogen pentoxide
5. Number of lithium ions, sulfate, ions, S atoms, and O atoms in 56.2 g of lithium sulfate

## 2. Calculate the percent by mass of the following compounds

1. $$SO_3$$
2. $$Pb(SO_4)_2$$

## 3. Determine the empirical and molecular formulas of each of the following substances:

1. Styrene contains 92.3% C and 7.7% H by mass and a molar mass of 104 g/mol
2. Caffeine contains 49.5% C, 5.15% H, 28.9% N, and 16.5% O by mass and has a molar mass of 195 g/mol
3. Monosodium glutamate contains 35.51% C, 4.77% H, 37.85% O, 8.29% N, and 13.60% Na, and has a molar mass of 169 g/mol.

## 4. Ethylene glycol

Ethylene glycol is used as an automobile antifreeze and in the manufacture of polyester fibers. Combustion of 6.38 g of ethylene glycol gives 9.06 g $$CO_2$$ and 5.58 g $$H_2O$$. The compound contains only $$C$$, $$H$$, and $$O$$. What is the empirical formula of the compound?

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