Moles Re-test

Front

What is a mole in chemistry?

Back

A mole is a unit of measurement used to express the amount of a substance. It is defined as the amount of substance that contains as many entities (atoms, molecules, etc.) as there are in 12 grams of carbon-12.

Front

How do you calculate the number of moles from mass?

Back

Number of moles = Mass (g) / Molar mass (g/mol).

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 find the empirical formula from percentage composition?

Back

1. Convert percentages to grams. 2. Convert grams to moles. 3. Divide by the smallest number of moles to find the 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). It is calculated by summing the atomic masses of all atoms in the formula.

Front

How many moles are in 75 grams of NaHCO₃?

Back

0.89 mol.

Front

What is the molar mass of CaCO₃?

Back

100.09 g.

Front

How do you determine the number of moles of carbon in a given mass of carbon?

Back

Use the formula: Number of moles = Mass of carbon (g) / Atomic mass of carbon (g/mol). For 5g of carbon, it is 0.42 mol.

Front

Which compounds have the same empirical formula: NaCrO₄ and Na₂Cr₂O₇, or C₂H₄O₂ and C₆H₁₂O₆?

Back

C₂H₄O₂ and C₆H₁₂O₆.

Front

What is the empirical formula for a compound with 72.2% magnesium and 27.8% nitrogen?

Back

Mg₃N₂.