4.2 Reactions of acids

Question 1

What happens when some metal reacts with an acid? What is this reaction?

Answer 1

A salt and hydrogen is produced; redox reaction.

Question 2

Types of strong acids and what they produce with metal.

Answer 2

• Hydrochloric acid (HCl): Metal chloride.
• Sulphuric acid (H₂SO ₄): Metal sulphate.
• Nitric acid (HNO₃): Metal nitrate.

Question 3

What happens when a metal oxide reacts with an acid?

Answer 3

Salt and water is produced.

Question 4

What happens when a metal carbonate reacts with an acid?

Answer 4

• Salts, water and carbon dioxide are produced.

Question 5

What neutralises acids

Answer 5

• Alkalis (soluble metal hydroxide)
• Bases (insoluble metal hydroxide, soluble metal oxides)
• Metal carbonates

Question 6

How can soluble salts be made?

Answer 6

Reacting an acid with solid insoluble substances (e.g. metal, metal oxide, metal hydroxide or carbonates)

Question 7

What do acids produce in aqueous solutions?

Answer 7

Hydrogen ions.

Question 8

What do aqueous solutions of alkali contain?

Answer 8

Hydroxide ions

Question 9

pH scale

Answer 9

Measure of acidity to alkalinity (0-14) of a solution, using a universal indicator of pH probe.

Question 10

Neutral pH

Answer 10

7

Question 11

pH value of aqueous solutions of acids

Answer 11

Less than 7

Question 12

pH value of aqueous solutions of alkalines

Answer 12

Greater than 7

Question 13

Neutralisation reaction

Answer 13

H⁺_(aq) + OH^-_(aq)—> H₂O_(l)

Question 14

How do different indicators measure pH value?

Answer 14

ACID —> ALKALINE

• Universal indicator: red - orange - yellow - green - blue - purple
• Methyl orange: red - yellow - yellow
• Phenolphthalein: colourless - pink
• Litmus paper: red - blue

Question 16

Strong acid

Answer 16

Completely ionised in aqueous solution.

Question 17

Weak acid

Answer 17

Partially ionised in aqueous solution.

Question 18

Types of weak acids.

Answer 18

• Ethanoic acid
• Citric acid
• Carbonic acid

Question 19

Dilute solution

Answer 19

Lower concentration of solute relative to solvent in solution.

Question 20

Concentrated solution.

Answer 20

Higher concentration of solute relative to solvent in solution.

Question 21

Relationship of pH and hydrogen ion concentration

Answer 21

As pH increases by one unit, hydrogen ion concentration increases by a factor of 10.

Question 22

Neutrality

Answer 22

Having the same number of hydrogen ions and hydroxide ions - pH 7.

Question 23

Relative acidity

Answer 23

Indicates a solution’s strength as an acid - the higher the hydrogen ion concentration, the lower the pH value, the stronger the acid.