3.1.4 - mixtures

Question 1

what is a mixture?

Answer 1

a mixture is made up of more than one substance, which are not chemically joined together

Question 2

what % of air is nitrogen?

Answer 2

78%

Question 3

what % of air is oxygen?

Answer 3

21%

Question 4

what % of air is argon?

Answer 4

0.96%

Question 5

what % of air is carbon dioxide?

Answer 5

0.04%

Question 6

how do you find the % of oxygen in air?

Answer 6

• by reacting it with another element, often a metal
• the air gradually decreases in volume until all the oxygen has been added to the element
  e.g heat copper until it turns into copper oxide when left in a tube and the volume of air would have decreased which shows you how much oxygen is in it

Question 7

what equation do you use to find the % of oxygen in air?

Answer 7

%O2 = (initial - final volume/intial volume) x 100

Question 8

what could cause the percentage of oxygen in air not be 21% in an experiment?

Answer 8

• metal wasn’t heated for long enough for all the oxygen to be reacted
• a leak in the apparatus

Question 9

what is a solution?

Answer 9

the resulting mixture of a solute dissolved in a solvent

Question 10

what is a solute?

Answer 10

the substance which is going to be dissolved

Question 11

what is a solvent?

Answer 11

the liquid which is going to do the dissolving

Question 12

what is saturated?

Answer 12

a solution in which no more solute can be dissolved

Question 13

what is suspension?

Answer 13

a solid floating in a liquid because it cannot dissolve

Question 14

what is soluble?

Answer 14

a substance which can be dissolved

Question 15

what is insoluble?

Answer 15

a substance which cannot be dissolved

Question 16

what do we measure solubility in?

Answer 16

g per 100g of solvent

Question 17

how can solubility be scaled?

Answer 17

can be scaled for different amounts of solvent

for example
36.37g/100g can be scaled to 18.185/50g by dividing by 2

Question 18

how does solubility vary with temp?

Answer 18

as temp increases solubility increases

Question 19

what does the line show on a solubility curve?

Answer 19

line = saturated
shows the max amount of solid which can be dissolved at each temp

Question 20

what does below the line show on a solubility curve?

Answer 20

below = soluble
less than the max mass of the solid, so it will all dissolve

Question 21

what does above the line show on a solubility curve?

Answer 21

above = insoluble
more than the max mass of solid, so some will dissolve and some won’t
the mass that dissolves can be found by reading off the line

Question 22

method to investigate solubility at a specific temp?

Answer 22

1. place a 100cm^3 beaker on a balance and zero it
2. add 20g of water
3. add 20g of copper sulphate crystals to water
4. stir mixture with thermometer for 2 mins
5. set up filter funnel over a 100cm^3 conical flask
6. while continuing to stir, gently heat mixture
7. as soon as it reacher allotted temp, pour it into filter
8. weigh conical flask and filtrate
9. pour filtrate away and reweigh conical flask