Chapter 12

Question 1

Measuring volume of liquids: measuring cylinder

Answer 1

Most useful in large amounts of solution -> not very accurate

Question 2

Measuring volume of liquids: volumetric pipette

Answer 2

Used to measure out single fixed volume of liquid -> accurate

Question 3

Measuring volume of liquids: Burette

Answer 3

Used to measure out volumes more accurately than a measuring cylinder

Question 4

Titrations (6 steps)

Answer 4

1) using pipette measure out a set volume of the alkali into a flask, and add a few drops of an indicator -> thymolpthalein or methyl orange
2) fill a burette with known concentration of acid
3) use burette to add acid to alkali a bit at a time, swirling the flask regularly
4) indicator changes colour when all alkali has been neutralised
5) record the volume of acid used to neutralise alkali
6) repeat process without indicator (no stain)

Question 5

Purity

Answer 5

. Pure: made up of a single elements or compound -> if more than one compound is a mixture
- Testing for purity
. If substances impure (mixture) then it will melt gradually over a range of temperatures
. Impurities: increase boiling points and decrease melting point

Question 6

Solution

Answer 6

Mixture of a solute and a solvent that doesn’t separate

Question 7

Solute

Answer 7

Substance that dissolves

Question 8

Solvent

Answer 8

Liquid solute dissolves into

Question 9

Saturated solution

Answer 9

Maximum amount of solute has been dissolved -> no more solute dissolves at that temperature

Question 10

Residue

Answer 10

Substance remaining at end of process of separation or purification

Question 11

Filtrate

Answer 11

Solution or a liquid that has been filtered

Question 12

Chromatography

Answer 12

Separates a mixture of soluble substances and identifies them -> works as different substances will move up paper at different rates

Question 13

Chromatography steps (4 steps)

Answer 13

1) add a spot of mixture to baseline (drawn in pencil) on chromatography paper
2) end of paper is placed in solvent with solvent, just below the baseline -> mixture should be soluble in solvent, and solvent shouldn’t react with mixture
3) solvent travels up the paper and carries substances in a mixture with it and these separate out -> further point reached by solvent is called solvent front
4) resulting pattern is called chromatogram -> you can compare it to a pure sample of a substance you might think is in the mixture to identify it
-> if mixture separates into colourless substances, spray locating agent onto paper to show where spots are

Question 14

Simple distillation

Answer 14

Separates out a liquid from a solution where different parts have very different boiling points

Question 15

Simple distillation (two steps)

Answer 15

1) solution heated in flask using a Bunsen burner and a part of solution that has lowest boiling point evaporates
2) vapour is cooled by a condenser, causing it to condense and it’s collected in a beaker -> rest of solution is left in flask

Question 16

Fractional distillation

Answer 16

Separates a mixture of liquids with similar boiling points

Question 17

Fractional distillation (six steps)

Answer 17

1) put mixture in a flask and put a fractionating column on top
2) heat mixture using Bunsen burner
3) different liquids will all have different boiling points SO they’ll evaporate at different temperatures
4) liquid with lowest boiling point evaporates and reaches top of column first
5) liquid with higher boiling point might also start to evaporate -> column is cooler towards top SO they’ll only get parts of way up before condensing and running back down into flask
6) when first liquid has been collected, raise temperature until next liquid reaches top

Question 18

Filtration

Answer 18

Separates an insoluble solid from a liquid

Question 19

Filtration (two steps)

Answer 19

1) put filter paper into a funnel and pour your mixture into it
2) liquid part of mixture runs through paper and leaves a solid residue -> wash, solid with distilled water and leave to dry

Question 20

Crystallisation

Answer 20

Separates a soluble solid from a solution

Question 21

Crystallisation (four steps)

Answer 21

1) pour solution into evaporating dish, and gently heat solution
2) some of water will evaporate and solution will get more concentrated
3) when you see crystals start to form (point of crystallisation) remove dish from heat and leave solution to cool
4) filter crystals out of solution and leave them in warm place to dry or use a drying oven

Question 22

Test for ions: test for ammonium ions (2 steps)

Answer 22

1) add sodium hydroxide solution to a solution being tested, and gently heat it
2) if ammonia gas is given off, it means that they’re ammonium ions in the solution -> test for ammonia gas by holding a piece of damp red litmus paper over it and see if it turns blue

Question 23

Test for ions: testing for metal ions using flame tests

Answer 23

1) clean nichrome wire loop by dipping it into hydrochloric acid and rinse it in distilled water
2) dip wire loop into a sample of metal compound and put loop in clear blue part of a Bunsen flame
3) record what colour flame goes