Topic 3 - Quantative Chemistry

Question 1

What does the relative atomic mass show

Answer 1

The mass of the element

Question 2

How do you find the relative formula mass ( mr) of a compound

Answer 2

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

Question 3

The total mass of the products in a reaction is equal to…

Answer 3

… the total mass of the reactants

Question 4

Atoms cannot be _______ or _________

Answer 4

Created or destroyed

Question 5

How can the princible of conservation of mass help you solve a chemical reaction

Answer 5

If you know 2 of the reactant + reactant = product, you can work out the other part because the reactants and product should be the same mass

Question 6

What’s the difference between reactions in a closed and non enclosed system?

Answer 6

No substances can enter or leave a closed system but can in an non enclosed system

Question 7

What is a solution

Answer 7

Mixture of a solvent and a solute

Question 8

What is a solute

Answer 8

The dissolved substance in a solution

Question 9

What is a solvent

Answer 9

The liquid in which the solute dissolves to form a solution

Question 10

Concentration g/dm cubed =

Answer 10

Mass of solute in g ÷ volume in dm cubed

Question 11

How can concentration be increased (2)

Answer 11

1.Dissolving more solute into solution
2.allowing some of the solvent to evaporate

Question 12

Percentage atom economy =

Answer 12

Total Mr of desired product ÷ total Mr of all reactants ×100

Question 13

What is the theoretical yield?

Answer 13

The maximum possible mass of a product that can be made in a chemical reaction

Question 14

Reasons why the mass of a product might be less than the maximum theoretical mass (3)

Answer 14

1. The reaction is reversible
2. Some if the product may be lost during the process
3. Some of the reactants may react in ways different to the expected reaction

Question 15

Percentage yield =

Answer 15

Mass of product actually made ÷ maximum theoretical mass of product × 100

Question 16

What are the 4 key features of a chemical reaction

Answer 16

1. compounds are broken up or formed
2. adleast 1 new substance is created
3. Measurable energy change
4. No atoms are created or destroyed

Question 17

Percentage mass of an element in a compound=

Answer 17

(Reletive atomic mass × number of atoms of that element ÷ Mr of the compound) × 100

Question 18

What is Avogadro constant?

Answer 18

6.02 × 10 ²³

Question 19

What is the mole and how many particles are in one mole?

Answer 19

The mole is the name given to the amount of a substance.

In one mole there’s 6.02 ×10 ²³ particles

Question 20

The number of moles in a mass =

Answer 20

Mass in g ÷ reletive formula mass

Question 21

How do you show that mass is conserved in a reaction?

Answer 21

Add up the reletive formula masses on each side and they should be the same number

Question 22

How can you balance equations using reacting masses? (4)

Answer 22

1)divide mass of each substance by its Mr to find number of moles
2)divide number of moles by smallest number of moles in reaction
3)if any numbers aren’t whole multiply all by the same number
4)write the balanced symbol equations by putting the numbers in front

Question 23

How to calculate theoretical yield (5)

Answer 23

1)write out balanced equation
2)calculate Mr
3)calculate number of moles
4) look at the ratio of moles in equation
5)calculate mass

Question 24

Volume of gass =

Answer 24

Mass of gas ÷ Mr of gas ×24