Topic 3 Qunatative

Question 1

What is relative atomic mass (Ar)?

Answer 1

The weighted average mass of an atom of an element compared to 1/12th the mass of a carbon-12 atom.

Question 2

What is a mole?

Answer 2

A mole is 6.02 × 10²³ particles (atoms, molecules, or ions) of a substance.

Question 3

How do you calculate the relative formula mass (Mr) of a compound?

Answer 3

Add up the relative atomic masses (Ar) of all atoms in the formula.

Example: Mr of H₂O = (2 × 1) + 16 = 18

Question 4

How do you calculate the number of moles?

Answer 4

Moles = mass (g) / mr

Question 5

What does the law of conservation of mass state?

Answer 5

Mass is conserved in a chemical reaction; total mass of reactants = total mass of products.

Question 6

How do you calculate the mass of a product or reactant?

Answer 6

1. Convert mass to moles.
2. Use the balanced equation to find the ratio.
3. Convert moles back to mass.

Question 7

What is a limiting reactant?

Answer 7

The reactant that is completely used up first, limiting the amount of product formed.

Question 8

How do you calculate concentration?

Answer 8

Concentration (g/dm3) =Mass (g) / volume (dm3)

Question 9

What volume does 1 mole of gas occupy at room temperature and pressure (RTP)?

Answer 9

24 dm3

Question 10

What is atom economy?

Answer 10

A measure of how much of the reactants end up as useful products the higher the more efficient.
Atom economy = Mr of useful product / Total Mr of reactants x100

Question 11

How do you calculate percentage yield?

Answer 11

Percentage yield = actual yield / theoretical yield X100

Question 12

What is the formula for titration calculations?

Answer 12

Moles= concentration (mol/dm3) x volume (dm3)