Acids and Bases

Question 1

What are acids?

Answer 1

Acids are substances that dissociate (break apart) when added to water to release hydrogen ions.

Question 2

What are the three common acids?

Answer 2

Hydrochloric acid: HCl
Nitric acid: HNO₃
Sulfuric acid: H₂SO₄

Question 3

What properties do the three common acids share?

Answer 3

• they are corrosive

- they taste sour

Question 4

What are the four types of bases you will need to know?

Answer 4

Metal oxides - a metal cation and oxide anion
Metal hydroxides - a metal cation and a hydroxide anion
Metal carbonate - a metal cation and a carbonate anion
Metal hydrogen carbonate - a metal cation and a hydrogen carbonate anion

Question 5

What are bases that are soluble in water called?

Answer 5

Alkalis, in water, alkalis form OH⁻ (hydroxide) ions.

Question 6

What two properties do alkalis share?

Answer 6

• they feel soapy on your tongue

- they have a bitter taste

Question 7

What happens when an acid meets an alkali?

Answer 7

when acids (which produce H+ ions) are mixed with alkali (which produce OH⁻ ions) water is made (H2O) 
This is called a neutralisation reaction.

Question 8

What is the pH scale?

Answer 8

pH is a scale of acidity from 0-14. It measures the relative concentration of H+ and OH- ions in water.

Question 9

What parts of the scale indicate whether it’s an acid, alkali or neutral substance?

Answer 9

Acidic solutions have a pH less than 7, alkali solutions have a pH scale above 7. Neutral substances have a pH of 7.

Question 10

Explain the parts of the pH scale

Answer 10

• Less acidic solutions have mostly H+ and some OH- ions.
• Very acidic solutions have almost all H+ and a a tiny amount of OH- ions.
• Neutral solutions have the same amount of H+ and OH- ions.
• Less alkali solutions have mostly OH- and some H+ ions.
• Very alkali solutions are almost all OH- and a tiny amount H+ ions.

Question 11

What are salts?

Answer 11

A salt is an ionic compound formed from the reaction of an acid and a base. The type of salt depends on the acid:
Hydrochloric acid: chloride
Nitric acid: nitrates
Sulfuric acid: sulfates

Question 12

What are the four possible reactions you will need to know? And what are the two different combinations products will these produce?

Answer 12

‘Acid + metal oxide’ and ‘acid + metal hydroxide’ produce a salt + water

‘Acid + metal carbonate’ and ‘Acid + metal hydrogen carbonate’ produce a salt + water + carbon dioxide
(tip to remember - the reactants with carbonate will produce carbon dioxide, any other will not)