Percent Composition Empirical Formulas Percent Composition Divide the

Percent Composition & Empirical Formulas

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: K 2 Cr. O 4 �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?

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.

Limiting Reactant Practice �Due TOMORROW! �Limting Reactant Lab – DUE TOMORROW

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 CO 2 gas is produced from burning 2804 g (1 gallon) of gasoline? Equation: 2 C 8 H 18 + 25 O 2 16 CO 2 + 18 H 2 O