Chemical Quantities Review

Front

What is percent composition?

Back

Percent composition is the percentage by mass of each element in a compound, calculated by dividing the mass of the element by the total mass of the compound and multiplying by 100.

Front

How do you calculate the percent composition of an element in a compound?

Back

To calculate percent composition, use the formula: (mass of element in 1 mole of compound / molar mass of compound) x 100.

Front

What is the empirical formula?

Back

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

Front

How do you determine the empirical formula from percent composition?

Back

Convert the percent composition to grams, then to moles, and find the simplest ratio of moles of each element.

Front

What is a molecular formula?

Back

The molecular formula shows the actual number of atoms of each element in a molecule of a compound.

Front

How do you find the molecular formula from the empirical formula?

Back

To find the molecular formula, divide the molecular mass by the empirical formula mass and multiply the subscripts in the empirical formula by that ratio.

Front

What is the molar mass of a compound?

Back

The molar mass is the mass of one mole of a substance, usually expressed in grams per mole (g/mol).

Front

What is the formula for magnesium phosphide?

Back

The formula for magnesium phosphide is Mg₃P₂.

Front

What is the percent by mass of magnesium in MgO?

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The percent by mass of magnesium in MgO is 60%.

Front

How do you calculate the percent by mass of an element in a compound?

Back

Percent by mass = (mass of element in 1 mole of compound / molar mass of compound) x 100.