chemical changes

Question 1

A strong acid is completely _______ in aqueous
solution.

Answer 1

ionised

Question 2

A weak acid is only _______ ionised in aqueous
solution

Answer 2

partially

Question 3

A weak acid (aq) has a lower pH than a strong acid (aq) of the same concentration. This is because ….

Answer 3

a weak acid has a lower concentration of hydrogen ions.

Question 4

Metal + acid →

Answer 4

salt + hydrogen

Question 5

Salts made when metals react with nitric acid are called ….

Answer 5

nitrates.

Question 6

Salts made when metals react with sulfuric acids are called ….

Answer 6

sulfates.

Question 7

Salts made when metals react with hydrochloric acid are called ….

Answer 7

chlorides.

Question 8

Making Soluble Salts from acids and alkalis =

Answer 8

Acid + Alkali → Salt + Water

Question 9

Making Soluble Salts from acids and bases =

Answer 9

Acid + Bases → Salt + Water

Question 10

Making Soluble Salts from acids and metal carbonates =

Answer 10

Acid + Metal carbonate → Salt + Water + Carbon dioxide

Question 11

what is a base?

Answer 11

Any substance that reacts with an acid to form a salt and water only.

Question 12

The test for hydrogen uses a burning splint held at the open end of a test tube of the gas. Hydrogen burns with a …..

Answer 12

pop sound.

Question 13

The test for carbon dioxide uses an aq solution of calcium hydroxide (lime water). When carbon dioxide is shaken or bubbled through limewater the limewater turns ….

Answer 13

milky (cloudy)

Question 14

1) Use the pipette to add 25 cm3 of alkali to a conical flask and add a few drops of indicator. 2) Fill the burette with acid and note the starting volume. Slowly add the acid from the burette to the alkali in the conical flask, swirling to mix.

Answer 14

3) Stop adding the acid when the end-point is reached (the appropriate colour change in the indicator happens). Note the final volume reading. Repeat steps 1 to 3 until you get consistent readings.

Question 15

Soluble salts can be made from acids by reacting them with ….

Answer 15

solid insoluble substances

Question 16

1) Measure the required volume of acid with a measuring cylinder and add the weighed solid (insoluble metal, oxide, hydroxide or carbonate) in small portions with stirring.
2) Safety goggles required - the mixture may be heated to speed up the reaction. When no more of the solid dissolves, it means ALL the acid is neutralised and there should be a little excess solid.

Answer 16

3) Filter the solution to remove the excess solid metal/oxide/carbonate into an evaporating dish. On filtration, only a solution of the salt is left.
4) Then hot concentrated solution is left to cool and crystallise.
5) After crystallisation, you collect and dry the crystals with a filter paper. If the solution is heated, the solvent will evaporate faster. Heating a solution until all the solvent has evaporated is known as heating to dryness.

Question 17

Insoluble salts can be made from ….

Answer 17

two soluble salts.