Quantitative Chemistry

What is relative formula mass (Mr)?

The total of the relative atomic masses (Ar) of all the atoms in a compound.

How do you calculate relative formula mass (Mr)?

Add together the Ar values of all the atoms in the formula.

What is the formula for calculating moles?

Moles = Mass (g) ÷ Mr

How do you calculate mass?

Mass = Moles × Mr

How do you calculate Mr?

Mr = Mass ÷ Moles

What is Avogadro's constant?

6.02 × 10²³ particles per mole.

How do you calculate the number of particles?

Particles = Moles × 6.02 × 10²³

How do you calculate moles from particles?

Moles = Particles ÷ 6.02 × 10²³

What is concentration in g/dm³?

Mass of solute per dm³ of solution.

How do you calculate concentration in g/dm³?

Concentration = Mass ÷ Volume (dm³)

How do you calculate concentration in mol/dm³?

Concentration = Moles ÷ Volume (dm³)

How do you calculate moles from concentration?

Moles = Concentration × Volume (dm³)

How do you convert cm³ to dm³?

Divide by 1000.

How do you convert dm³ to cm³?

Multiply by 1000.

What volume does 1 mole of gas occupy at RTP?

24 dm³.

How do you calculate moles of a gas at RTP?

Moles = Volume (dm³) ÷ 24

How do you calculate gas volume at RTP?

Volume = Moles × 24 dm³

What is a balanced symbol equation?

An equation with the same number of each type of atom on both sides.

Why are balanced equations important?

They show the correct mole ratios for calculations.

What is a mole ratio?

The ratio of substances shown by the coefficients in a balanced equation.

What is the limiting reactant?

The reactant that is used up first and stops the reaction.

What is the excess reactant?

The reactant left over after the reaction finishes.

What is theoretical yield?

The maximum amount of product that can be made.

What is actual yield?

The amount of product actually produced.

How do you calculate percentage yield?

(Actual Yield ÷ Theoretical Yield) × 100

Why is percentage yield usually less than 100%?

Products may be lost, reactions may be reversible, or side reactions may occur.

What is atom economy?

A measure of how many reactant atoms end up in the desired product.

How do you calculate atom economy?

(Mr of desired product ÷ Total Mr of all products) × 100

Why is a high atom economy desirable?

It produces less waste and is more sustainable.

What are the four steps in mole calculations?

Calculate moles of the known substance, use the mole ratio, calculate moles of the unknown substance, then convert to mass or volume if needed.