3.1.4 - mixtures Flashcards
what is a mixture?
a mixture is made up of more than one substance, which are not chemically joined together
what % of air is nitrogen?
78%
what % of air is oxygen?
21%
what % of air is argon?
0.96%
what % of air is carbon dioxide?
0.04%
how do you find the % of oxygen in air?
- 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
what equation do you use to find the % of oxygen in air?
%O2 = (initial - final volume/intial volume) x 100
what could cause the percentage of oxygen in air not be 21% in an experiment?
- metal wasn’t heated for long enough for all the oxygen to be reacted
- a leak in the apparatus
what is a solution?
the resulting mixture of a solute dissolved in a solvent
what is a solute?
the substance which is going to be dissolved
what is a solvent?
the liquid which is going to do the dissolving
what is saturated?
a solution in which no more solute can be dissolved
what is suspension?
a solid floating in a liquid because it cannot dissolve
what is soluble?
a substance which can be dissolved
what is insoluble?
a substance which cannot be dissolved
what do we measure solubility in?
g per 100g of solvent
how can solubility be scaled?
can be scaled for different amounts of solvent
for example
36.37g/100g can be scaled to 18.185/50g by dividing by 2
how does solubility vary with temp?
as temp increases solubility increases
what does the line show on a solubility curve?
line = saturated
shows the max amount of solid which can be dissolved at each temp
what does below the line show on a solubility curve?
below = soluble
less than the max mass of the solid, so it will all dissolve
what does above the line show on a solubility curve?
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
method to investigate solubility at a specific temp?
- place a 100cm^3 beaker on a balance and zero it
- add 20g of water
- add 20g of copper sulphate crystals to water
- stir mixture with thermometer for 2 mins
- set up filter funnel over a 100cm^3 conical flask
- while continuing to stir, gently heat mixture
- as soon as it reacher allotted temp, pour it into filter
- weigh conical flask and filtrate
- pour filtrate away and reweigh conical flask
