Percent Composition Divide the mass of each element

by the molar mass of the compound and multiply by 100

Can be found from the formula OR experimental data

Potassium Chromate Formula: K2CrO4

Potassium:

Chromium:

Oxygen:

Potassium Chromate

Experimental Data A 0.2370 g sample of an unknown compound is

extracted from the roots of a plant. Decomposition of the sample produces 0.09480 g of carbon, 0.1264 g of oxygen, and 0.0158 g of hydrogen. What is the percent composition of the compound?

Experimental Data

Empirical Formula

The simplest whole number ratio of a compound

Empirical Formula 1) Turn mass into moles for each

element

2) Divide all mole amounts by the smallest one

3) Write the formula using the whole number mole amounts as subscripts

Practice Problem

Find the empirical formula for the compound in the experimental data above.

Step 1 Turn mass into moles for each element.

Step 2 Divide all mole amounts by smallest number

Step 3 Write the formula using the whole number mole

amounts as subscripts.

Warm-Up • Answer these questions on the back of your

Warm-Up Sheet from before break. DO NOT write the prompts. DO show your work.

1) What is the mass (in grams) of exactly one water molecule?

2) What volume of CO2 gas is produced from burning 2804 g (1 gallon) of gasoline?

Equation: 2 C8H18 + 25 O2 16 CO2 + 18 H2O