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chemistry > solubility/diffusion/ separating mixtures > Flashcards

solubility/diffusion/ separating mixtures Flashcards

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1
Q

Explain how you know that a solid is soluble in a solvent in terms of forces of attraction

A
  • If new attractive forces formed between solute and solvent

- are strong enough to overcome the old ones between the solute

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2
Q

Explain the 6 major steps in an experiment of investigating solubility of a solute in solvent

A
  • measure basin
  • heat boiling tube and allow solute to dissolve until no more solute can dissolve
  • pour solution into evaporating basin and weigh basin now
  • heat solution to evaporate all water until heated to a constant mass
  • measure the solute and the basin
  • calculate mass of solute/mass of solvent x 100
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3
Q

If you have s solution of 148g dissolved in water at 80 degrees, and it cools down to room temperature 20 degrees which now has a mass of 86g, what will happen. (3)

A
  • Solubility decreases
  • 62 grams will come out as crystals.
  • It precipitates.
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4
Q

What is the maximum mass of a substance that will dissolve in 50 grams of water if at 40 degreees it dissolves 40 grams

A

20grams

Because 40/20

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5
Q

Why is diffusion through a liquid slower than diffusion through a gas

A

Because particles move much slower

- and are more closely packed so there is less space for particles to move

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6
Q

In diffusion experiment of ammonia and hydrochloride acid, why is the white ring further away from the ammonia

A

Because ammonia particles are lighter and so travel faster

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7
Q

Why does adding more water to potassium manganate make it paler

A

Because the particles are now more widely spread out

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8
Q

Why does diffusion happen quickly in gases

A

Because the particles have are more widely spread so have more space AND are able to move quicker

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9
Q

If the solute is white then why is the solution colorless

A

Because the particles break apart

- and spread out through the water

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10
Q

Why is dilution slow in liquids

A

Because the particles are more closely packed AND because they move slower

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11
Q

Explain how diffusion happens in liquids with the example of potassium manganate and water

A

Potassium manganate and water particles are moving randomly so their particles are able to slide over each other
Particles can therefore easily mix
Concentration of particles are now evenly spread

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12
Q

In paper chromatography where is the original spot placed

A

Placed on the baseline

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13
Q

Is calcium carbonate (chalk) soluble in water

A

No

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14
Q

Is calcium carbonate (chalk) soluble in water

A

No

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15
Q

If you want to separate pure water from sea water what technique would you use

A

Simple distillation

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16
Q

If you want to separate pure water from sea water what technique would you use

A

Simple distillation

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17
Q

Is copper sulfate soluble or insoluble in water(it is a salt)

A

Soluble

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18
Q

Is copper sulfate soluble or insoluble in water(it is a salt)

A

Soluble

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19
Q

What is the meaning of aqueous

A

The solvent is water

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20
Q

What are two reasons we put a lid on chromatography

A

To avoid evaporation

To avoid toxic fumes from escaping

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21
Q

How do you know if a substance is aqueous or a liquid

A

Aqueous if a precipitate, water, or ions are involved

22
Q

What is a precipitate

A

The insoluble solid that forms from a liquid solution

23
Q

How can you obtain a pure dry sample of crystals from a solution (4)

A

1) heat to evaporate water
2) leave to crystallize
3) filter to remove access liquid
4) dry with kitchen paper

24
Q

Why do crystals form when a hot saturated solution is cooled

A

Because of the temperature decrease, the solubility decreases

25
Q

Describe what you should do as soon as you place the spots on the chromatogram

A
  • Place paper in beaker, solvent level should be below
  • seal the container
  • wait until the solvent reaches the top of the paper
26
Q

Why would you leave a solid in a warm place to dry

A

To increase the rate of evaporation

27
Q

What do the glass rods in the fractionating column do?

A

Provides a large surface area which condenses the gases that rise

28
Q

3 main Steps in fractional distillation if you have three liquids to separate

A

1) first liquid with lowest boiling point evaporates and condenses
2) other liquids may evaporate by chance but will condense back into flask
3) temperature will be altered for substance of the second lowest boiling point

29
Q

If they ask you to draw the different dyes in a chromatography experiment , what must you include in your diagram

A

Labels

30
Q

What separation method would you use to separate water FROM a solution of copper sulfate and water

A

Simple distillation

Because solvent form solute

31
Q

Why would you mix sodium chloride and heat it when trying to dissolve

A

1) to dissolve sodium chloride

2) More quickly

32
Q

Name one reason that crystallization is better than evaportaion

A

Upon heating, Bunsen burner could cause the solute to thermally decompose in evaportion,
But crystallization uses a water bath which is much more gentle

33
Q

A student is making hydrated copper sulfate crystals
1)He first heats sulfuric acid
2)He then adds copper oxide to the sulfuric acid until the copper oxide is in excess
3)then he filters the mixture
Explain why he filters the mixture in step three

A

To remove the excess copper oxide

remeber that the copper oxide will stick to the filter paper and the copper sulphate solution will pass through

34
Q

A liquid solution of copper sulfate is cooled to form hydrated copper sulfate crystals.
Explain why crystals form when the hot saturated solution is cooled (2)

A

1) solubility decreases in cooler temperatures

2) so an ionic lattice is formed

35
Q

After a student has placed the dots of food coloring on the chromatography paper, explain three more things she needs to do in order to complete the experiment

A

1) move paper into the solvent so that solvent level is slightly below the spots
2) place a lid on it and wait for the solvent level to reach the top of the paper
3) leave to dry

36
Q

Explain how the diffusion of potassium manganate (VII) occurs with water

A

Crystals diffuse from high concentration to low concentration
Because there are gaps between the particles, and because particles in a liquid are able to slide over each other
So they can thus easily mix with each other

37
Q

Give formula for RF value

A

Distance travelled by solute/ distance travelled by solvent

38
Q

State the names of three experiments that can be used to show diffusion

A

Potassium magnate (VII) in water
Ammonia gas and hydrogen chloride gas
Bromine gas and air

39
Q

In the ammonia and hydrogen chloride gas experiment to demonstrate diffusion, state the solution that each cotton wool is soaked in

A

Ammonium
Hydrochloric acid

40
Q

Explain the diffusion between bromine gas and air

A

Bromine gas is able to diffuse from high concentration to low concentration
Because of the random movement of particles of a gas, and because there are large gaps between them

41
Q

Give the equation for finding solubility

A

Solubility = (mass of solute/mass of solvent) x100

42
Q

As temperature increases,
Describe what happens to the solubility of a gas
And what happens to the solubility of a solid

A

Solubility of a gas decreases
Solubility of a solid increases

43
Q

Explain the experiment to investigate the solubility at different temperatures

A

1)heat a boiling tube and add in excess solute to it until solution become saturated
2)allow it to cool to ensure that all the excess has sunk to the bottom
3)weigh an empty evaporating basin
4)add to it only the solution, making sure no solid is added to it
5)weigh the basin with the soltuion
6)heat until all the water has evaporated, and then weight just the absinthe and the dry crystals
7)reheat and resign, which is called heating to a constant mass to ensure that all the water has been evaporated
8)repeat for different temperatures
9)to find solubility, find the mass of solute dissolved and the solvent it took

44
Q

During fractional distillation, what happens if some of the other liquids with high boiling points also start to evaporate whilst the ones with the lowest boiling point is already evaporating

A

Because the column is coolest near the top,
Once they reach the top, These liquids with high boiling points will reach a temperature lower than their boiling point, so will begin to condense back into a liquid and will drop back down into the flask

45
Q

Why does the RF value have no units

A

Because it’s a ratio

46
Q

A substance has RF value of 0.8
Another has a Rf value of 0.2
Explain their solubilities

A

0.8 has RF Closer to 1 so more soluble
0.2 has RF closer to 0 so less soluble

47
Q

In paper chromatography, state three things u mist do to ensure reliable results

A

Make sure pencil line is above solvent so that the inks don’t automatically get washed away
Make sure u draw in pencil, because it’s insoluble so won’t dissolve in solvent
Place a lid on it to stop it from evaporating

48
Q

In paper chromatography, from the results, how do u know if a substance is pure or impure

A

Pure substance will produce only one spot
Impure substances will produce more than one spot

49
Q

Paper chromatography is used to separate….

A

Soluble mixtures

50
Q

Miscible means

A

When two liquids can be mixed with each other

51
Q

When temperature increases, why does solubility…, for a solid

A

Increase
This is because the solvent molecules have more kinetic energy
So can more efficiently break apart the solute molecules which are held together by intermolecular forces of attraction

52
Q

What is rock salt made up of

A

Sand and salt

chemistry (18 decks)

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