Solubility

Question 1

Define solute

Answer 1

a substance that dissolves

Question 2

Define soluble

Answer 2

a substance that can dissolve

Question 3

Define insoluble

Answer 3

a substance that cannot dissolve

Question 4

Define solvent

Answer 4

the substance where a solute dissolves in

Question 5

Define solubility

Answer 5

the maximum mass of a substance that can dissolve in a solvent

Question 6

Define saturated

Answer 6

a mixture in which no more solute can dissolve

Question 7

Define solution

Answer 7

a mixture that of a solute and a solvent

Question 8

Define suspension

Answer 8

an insoluble solute in a liquid

Question 9

Define dissociate

Answer 9

particles separate (no longer touching)

Question 10

What is solubility measured in?

Answer 10

g/100 cm³

Question 11

Which factor affects solubility?

Answer 11

temperature

Question 12

Why is a solid easier to dissolve in higher temperatures?

Answer 12

because when heated, the solid’s particles dissociate. this process requires lots of energy (gained from heating) to break the strong bonds between particles

Question 13

Why is a gas harder to dissolve in higher temperatures?

Answer 13

because when heated, the gas’s particles spread out even more than they were before, making it harder to dissolve.

Question 14

What is the general method for measuring solublility?

Answer 14

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)

Question 15

Why might distillation be used?

Answer 15

to separate any solid from a liquid and collect the solvent

Question 16

If the solute is insoluble, what other technique other than distillation can be used to separate the solute and solvent?

Answer 16

filtering

Question 17

Give an example of distillation

Answer 17

desalination (producing fresh water from sea water)

Question 18

When 2 liquids are mixed together, fractional distillation can also be used if:
1)
2)

Answer 18

1) liquids are miscible

2) liquid have different bpt

Question 19

Define miscible

Answer 19

form one fase

Question 20

What is distillation with 2 liquids called?

Answer 20

fractional distillation

Question 21

What is the bpt of propanone?

Answer 21

60 ºc

Question 22

What is the bpt of water?

Answer 22

100 ºc

Question 23

Describe fractional distillation using propanone and water (Page 15)

Answer 23

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

Question 24

How are immiscible liquids separated?

Answer 24

separating funnel

Question 25

What 2 methods are used to separate miscible liquids and why?

Answer 25

1) fractional distillation → dif. bpt

2) chromatography → dif. solubilities

Question 26

Describe the written method for chromatography

Answer 26

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

Question 27

Why do the particles of the components separate in chromatography?

Answer 27

because each component has a difference attraction to the solvent particles (key interaction). if there is a stronger attraction, the particles move further

Question 28

How is Rf (retention factor) calculated in terms of chromatography?

Answer 28

distance of component/distance of solvent

Question 29

Define diffusion

Answer 29

the random movement of particles that causes them to spread out and mix

Question 30

What are the 4 stages of a solid (KMnO₄) dissolving in a solvent (water)?

Answer 30

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

Question 31

What 2 factors does that rate of diffusion depend on?

Answer 31

• temperature
• size / mass of particles

Question 32

Why does increasing the temperature increase the rate of diffusion?

Answer 32

because the particles gain energy and move faster

Question 33

Compare large and small particles. Which diffuse faster?

Answer 33

smaller particles

Question 34

Why are precipitation reactions used?

Answer 34

to show the movement of particles during diffusion

Question 35

Describe an easy experiment to test rate of diffusion

Answer 35

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

Question 36

What are the results for the diffusion test with ammonia and hydrogenchloride?

Answer 36

NH₃ diffuses faster than HCl

Question 36

Why do ammonia particles diffuse faster than hydrogenchloride particles?

Answer 36

because they are smaller