Acids And Alkalis

Question 1

What was Arrhenius’ theory?

Answer 1

That when mixed with water, all acids release hydrogen ions and that alkalis form OH- ions (hydroxide ions) when in water.

Question 2

What was the exception with Arrhenius’ idea?

Answer 2

Ammonia gas can act as a base even when it isn’t dissolved in water.

Question 3

Lowry and Bronsted said acids…

Answer 3

Release H+ ions i.e. They are proton donors

Question 4

Lowry and Bronsted said alkalis…

Answer 4

Accept H+ ions i.e. They are proton accepters.

Question 5

For a substance to act as an acid or base you usually need water, what happens in acidic solutions?

Answer 5

The acid molecules dissociate releasing lots of H+ ions. These H+ ions (protons) become hydrated (surrounded by water molecules). The protons are now hydrated protons (H+ (aq)) and these are what makes acids acidic.

Question 6

For a substance to acts as an acid or base you usually need water, what happens in basic solutions?

Answer 6

Water molecules can dissociate into H+ and OH- ions. Some base molecules like ammonia can take hydrogen ions from water causing more to dissociate and leaving excess OH- ions behind. Other bases like potassium hydroxide release hydroxide ions straight into the solution.

Question 7

Strong acids ionise…

Answer 7

Almost completely in water so almost every hydrogen atom becomes a hydrated proton.

Question 8

Weak acids ionise…

Answer 8

Only very slightly so only small numbers of H+ ions are formed.

Question 9

Phenolphthalein

Answer 9

Is used for a weak acid and strong alkali, pink in alkalis, colourless in acids.

Question 10

Methyl orange

Answer 10

Is used for a strong acid and weak alkali.

Question 11

Titration equipment

Answer 11

Flask, burette,