Chemical Quantities Review

Front

What is the percent composition of an element in a compound?

Back

The percent composition of an element in a compound is the percentage by mass of that element in the total mass of the compound.

Front

How do you calculate the percent composition of Nitrogen in NO₂?

Back

Percent composition of Nitrogen in NO₂ = (mass of N in NO₂ / molar mass of NO₂) x 100 = (14.01 g / 46.01 g) x 100 ≈ 30%.

Front

What is the percent composition of Carbon and Hydrogen in Benzene (C₆H₆)?

Back

C = 92.2%, H = 7.8%.

Front

What is an empirical formula?

Back

An empirical formula is the simplest whole-number ratio of atoms of each element in a compound.

Front

What is the empirical formula of C₃H₆?

Back

The empirical formula of C₃H₆ is CH₂.

Front

How do you determine if two compounds have the same empirical formula?

Back

Two compounds have the same empirical formula if they can be reduced to the same simplest ratio of elements.

Front

Which pair has the same empirical formula: NaCrO₄ and Na₂Cr₂O₇ or C₂H₄O₂ and C₆H₁₂O₆?

Back

C₂H₄O₂ and C₆H₁₂O₆ have the same empirical formula.

Front

What is the molar mass of O₂?

Back

The molar mass of O₂ is 32 g/mol.

Front

How many moles are in 64 grams of O₂?

Back

Number of moles = mass (g) / molar mass (g/mol) = 64 g / 32 g/mol = 2 moles.

Front

What is the formula to calculate moles from mass?

Back

Moles = Mass (g) / Molar Mass (g/mol).