Molar Mass

Molar mass is a measure of the mass of a given substance (chemical element or chemical compound) divided by the amount of substance. It is expressed in units of grams per mole (g/mol). Molar mass is an essential concept in chemistry as it allows us to convert between the mass of a substance and the number of moles of that substance.

Calculating Molar Mass

The molar mass of an element is simply its atomic mass from the periodic table expressed in grams per mole. For example, the molar mass of carbon (C) is 12.01 g/mol. For compounds, the molar mass is calculated by adding up the atomic masses of all the atoms in the compound according to its chemical formula. For instance, the molar mass of water (H₂O) is calculated as follows:

Molar mass of H₂O = 2(1.01 g/mol) + 16.00 g/mol = 18.02 g/mol

Importance of Molar Mass

Molar mass is crucial in various chemical calculations, such as determining the amount of a substance in moles given its mass, or finding the mass of a substance given the number of moles. It is also used in stoichiometry, which involves the calculation of reactants and products in chemical reactions.

Practice Problems

1. Calculate the molar mass of carbon dioxide (CO₂).

2. Find the molar mass of calcium chloride (CaCl₂).

3. Determine the molar mass of sulfuric acid (H₂SO₄).

Answers

1. Molar mass of CO₂ = 12.01 g/mol (C) + 2(16.00 g/mol) (O) = 44.01 g/mol

2. Molar mass of CaCl₂ = 40.08 g/mol (Ca) + 2(35.45 g/mol) (Cl) = 110.98 g/mol

3. Molar mass of H₂SO₄ = 2(1.01 g/mol) (H) + 32.06 g/mol (S) + 4(16.00 g/mol) (O) = 98.08 g/mol

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