chapter 8 - acid and bases (part two ; bases)

Question 1

definition of alkali

Answer 1

a substance that ionises in water to form hydroxide ions, OH-

Question 2

definition of a weak alkali

Answer 2

a substance that ionises partially when dissolved in water to form hydroxide ions

Question 3

definition of a strong alkali

Answer 3

a substance that ionises completely when dissolved in water to form hydroxide ions

Question 4

name the 4 physical properties of alkalis

Answer 4

1. taste bitter
2. turn red litmus paper blue
3. pH more than 7
   (concentration of OH- is greater than concentration of H+)
4. can conduct electricity due to free moving ions

Question 5

name the 2 chemical properties of alkali

Answer 5

1. reacts with ammonium salts to form salt + water + ammonia
2. reacts with acid to form salt + water

Question 6

formula when alkalis react with acids

Answer 6

alkali + acid –> salt + water

Question 7

what happens when alkalis react with acids?

Answer 7

neutralization occurs

the hydrogen ions from the acid, H+, and the hydroxide ions from the alkali, OH-, react to form water

Question 8

formula when alkalis react with ammonium salts

Answer 8

alkali + ammonium salt –> salt + water + ammonia

Question 9

what happens when alkalis react with ammonium salts?

Answer 9

when alkalis are heated with ammonium salts,
they give off ammonia gas

Question 10

how can we test for ammonia gas?

Answer 10

with a piece of damp red litmus paper

ammonia gas turns the damp red litmus paper blue