STC 112 Theory Questions: Determining Molecular and Empirical Formulas in Chemistry

100 Level Science Technology Department exam questions and detailed answers. Download the answers in document format. Correct, detailed, and straightforward answers.

Questions:

a. What is the molecular formula of each compound?
i. An oxide of nitrogen contains 30.45 mass % N.
ii. Empirical formula NH₃ (Mm = 32.05 g/mol).

b. Determine the empirical formula of each of the following compounds.
i. 0.039 mol of iron atoms combined with 0.052 mol of oxygen atom.
ii. 0.903 g of phosphorus combined with 6.99 g of bromine
iii. A hydrocarbon with 79.9 mass % of carbon.

c. Benzo[a]pyrene (Mm = 252.30 g/mol); analysis of this hydrocarbon shows 95.21 mass % C and 4.79 mass % H. What is the molecular formula of benzo[a]pyrene?

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