GCSE WJEC Chemistry- acids, salts and bases

group of elements present in alkalis

OH → Hydroxide

1-6 PH scale

strong + weak end

acid

1= strong

6= weak

7 PH scale

neutral

8-14 PH scale

strong + weak end

alkali

8= weak

14= strong

element present in acids

H → Hydrogen

acid turns litmus paper

red

alkali turns litmus paper

blue

standard neutralisation equation

H⁺ + OH⁻ → H₂O

base

any metal oxide/ hydroxide

1st part salt name

2nd part salt name

1st= comes from equation

2nd= acid used

acid + metal

salt + hydrogen

acid + base

salt + water

acid + alkali

salt + water

acid + carbonate

salt + water + CO₂

hydriochloric acid gives…

chlorides

sulfuric acid gives…

sulfates

nitric acid gives…

nitrates

how to identify sulfate ions

test with barium chloride → creates white preticipate

what is neutralisation?

when an acid and an alkali cancel each other out

titration method

use solution of known concentration- react with solution of unknown concentration

• acid added to alkali until indicator turns colour (phenophthalein is pink in alkali + colourless in acid)

• volume of acid needed is recorded

  • burette is used and offers great precision

method for preparing crystals of a soluble salt from the reaction of insoluble bases/ carbonates and dilute acids

1) gradually add the base/ carbonate in excess

2) gently heat mixture + stir to ensure max reaction

3) the excess is removed by filtration using filter funnel + filter paper

4) the filtered solution is put in an evaporating basin and left (near a window) at room temp

5) water evaporates and crystals of the salt are formed in the evaporating basin