Solubility Flashcards
Define solute
a substance that dissolves
Define soluble
a substance that can dissolve
Define insoluble
a substance that cannot dissolve
Define solvent
the substance where a solute dissolves in
Define solubility
the maximum mass of a substance that can dissolve in a solvent
Define saturated
a mixture in which no more solute can dissolve
Define solution
a mixture that of a solute and a solvent
Define suspension
an insoluble solute in a liquid
Define dissociate
particles separate (no longer touching)
What is solubility measured in?
g/100 cm³
Which factor affects solubility?
temperature
Why is a solid easier to dissolve in higher temperatures?
because when heated, the solid’s particles dissociate. this process requires lots of energy (gained from heating) to break the strong bonds between particles
Why is a gas harder to dissolve in higher temperatures?
because when heated, the gas’s particles spread out even more than they were before, making it harder to dissolve.
What is the general method for measuring solublility?
1) measure x cm³ of solvent in a measuring cylinder
2) add excess solid (x g)
3) heat to speed up reaction and evaporate water (solubility increases)
4) let it cool down a bit
5) filter and collect residue (y g)
x - y = solubility
(find example of page 9, marked with an orange post-it)
Why might distillation be used?
to separate any solid from a liquid and collect the solvent
If the solute is insoluble, what other technique other than distillation can be used to separate the solute and solvent?
filtering
Give an example of distillation
desalination (producing fresh water from sea water)
When 2 liquids are mixed together, fractional distillation can also be used if:
1)
2)
1) liquids are miscible
2) liquid have different bpt
Define miscible
form one fase
What is distillation with 2 liquids called?
fractional distillation
What is the bpt of propanone?
60 ºc
What is the bpt of water?
100 ºc
Describe fractional distillation using propanone and water (Page 15)
1) propanone evaporates, water does not evaporate as insufficient energy is applied
2) temp. should be at the bpt of the first liquid, propanone (60 ºc)
3) propanone enters condenser. propanone particles lose energy, they slow down and start to slide over each other. from spread out to touching
4) pure propanone is collected in the beaker
How are immiscible liquids separated?
separating funnel
What 2 methods are used to separate miscible liquids and why?
1) fractional distillation → dif. bpt
2) chromatography → dif. solubilities
Describe the written method for chromatography
1) place ~2 cm³ of solvent in a beaker
2) draw a pencil line 2.5 cm from the bottom of the chromatography paper (base-line)
3) place one drop of mixture on baseline
4) stand paper in solvent and cover beaker
5) leave until solvent is around 1 cm³ from top
6) draw a pencil to show solvent distance (solvent front)
7) dry paper with hot-plate
Why do the particles of the components separate in chromatography?
because each component has a difference attraction to the solvent particles (key interaction). if there is a stronger attraction, the particles move further
How is Rf (retention factor) calculated in terms of chromatography?
distance of component/distance of solvent
Define diffusion
the random movement of particles that causes them to spread out and mix
What are the 4 stages of a solid (KMnO₄) dissolving in a solvent (water)?
1) particles of the solid dissociate and dissolve in the water
2) water particles dissociate and solid slides over each other and mixes
3) the random movement of particles causes them to spread out
4) once “equally spaced”, the particles continue to move randomly but there is no change in net movement
What 2 factors does that rate of diffusion depend on?
- temperature
- size / mass of particles
Why does increasing the temperature increase the rate of diffusion?
because the particles gain energy and move faster
Compare large and small particles. Which diffuse faster?
smaller particles
Why are precipitation reactions used?
to show the movement of particles during diffusion
Describe an easy experiment to test rate of diffusion
1) place a cotton wool dipped in NH₃ and another dipped in HCl at different ends of a tube
2) observe where white solid forms
What are the results for the diffusion test with ammonia and hydrogenchloride?
NH₃ diffuses faster than HCl
Why do ammonia particles diffuse faster than hydrogenchloride particles?
because they are smaller
