P1. Topic 3- Quantitative Chemistry (calculations) 🥇

Question 1

Law of conservation of mass

Answer 1

Mass cannot be created or destroyed in a chemical reaction.

Question 2

What does the 4 in CH₄ represent

Answer 2

There are four hydrogen atoms in the molecule.

Question 3

What does the 3 in 3H₂O represent

Answer 3

There are three water molecules.

Question 4

What is Mr

Answer 4

Relative formula mass

Question 5

What is Relative formula mass

Answer 5

The sum of the relative atomic masses of all the atoms in a compound.

Question 6

How do you calculate the relative formula mass

Answer 6

Add together the relative atomic masses of all atoms in the formula.

Question 7

How to calculate the percentage of mass in an element

Answer 7

(Ar of the element × number of atoms ÷ Mr of the compound) × 100.

Question 8

How does the mass of a metal change when it reacts with oxygen

Answer 8

It increases because it gains oxygen.

Question 9

How does mass of a metal carbonate change when it thermally decomposes

Answer 9

It decreases as carbon dioxide is lost.

Question 10

What is the uncertainty

Answer 10

An estimate of the range within which the true value lies.

Question 11

How to calculate the percentage uncertainty

Answer 11

(uncertainty ÷ measured value) × 100.

Question 12

Chemical symbol for moles

Answer 12

n

Question 13

Number of particles in a mole

Answer 13

Avogadro’s constant.

Question 14

Particles in one mole of a substance (Avogadro)

Answer 14

6.022 × 10²³ (you get this in the paper)

Question 15

What is a mole

Answer 15

A unit of measurement

Question 16

Limiting reactant

Answer 16

The reactant that is completely used up in a reaction

Question 17

Limiting reactant in a chemical reaction

Answer 17

It is used up first, stopping the reaction.

Question 18

Excess reactant

Answer 18

The reactant that is not limiting in a chemical reaction, the remaining reactant that is left behind as an excess

Question 19

Solution

Answer 19

A mixture of a solute dissolved in a solvent.

Question 20

Concentration of a solution

Answer 20

Mass of solute ÷ volume of solution. Remember conc= mol/vol

Question 21

Standard unit for measuring concentration

Answer 21

g/dm³.

Question 22

Conversion between cm³ and dm³

Answer 22

1 dm³ = 1000 cm³.

Question 23

Mass of a solute and volume of a solvent relation to concentration

Answer 23

Higher mass or lower volume = higher concentration.

Question 24

Yield of a reaction

Answer 24

The amount of product obtained compared to the maximum possible.

Question 25

Give some Reasons for not achieving expected yield

Answer 25

Reversible reactions, side reactions, loss during transfer.

Question 26

Percentage yield formula

Answer 26

(actual yield ÷ theoretical yield) × 100.

Question 27

Atom economy

Answer 27

How much of the reactants end up as useful products.

Question 28

Importance of atom economy in industry

Answer 28

Reduces waste and costs.

Question 29

Atom Economy formula

Answer 29

(RFM of desired products ÷ RFM of all products) × 100.

Question 30

Room temperature and pressure

Answer 30

20°C and 1 atmosphere.

Question 31

Volume of one mole of gas at room temperature and pressure

Answer 31

24 dm³.

Question 32

How to calculate a mole

Answer 32

Moles= Mass/ Mr (n=m/mr)

Question 33

How to calculate volume of a gas

Answer 33

Volume of gas= moles/ 24 dm³. Or mass of gas/Mr of gas x24

Question 34

What should you do first when calculating

Answer 34

Conversions (Kg -> g | Cm³ -> dm³)