C5 - Chemical Changes (titrations)

Question 1

Reactions:
1. Metal + acid
2. Metal hydroxide + acid
3. metal carbonate + acid
4. Metal + water
5. Metal + oxygen

Answer 1

1. Salt + hydrogen
2. Salt + water
3. Salt + water + carbon dioxide
4. Metal hydroxide + hydrogen
5. Metal oxide

Question 2

Neutralisation ionic equation

Answer 2

OH- + H+ —> H2O

Question 3

Strong vs weak vs dilute acids

Answer 3

Strong - Completely ionise in solution. High concentration of H+ ions in the acid

Weak - Don’t completely ionise in solution - reversible reactions. (Carboxyllic acids)

Dilute - low concentration of acid in water

As H+ concentration x10, pH decreases by 1

Question 4

Salt endings + charges

Answer 4

• OH^- (hydroxide)
• NO3^- (nitrate)
• SO4^2- (Sulfate)
• CO3^2- (carbonate)

Question 5

What are alkalis

Answer 5

Soluble bases
pH greater than 7
Dissociate into OH- ions in solution

Question 6

What are the units for concentration?

Answer 6

g/dm3 and mol/dm3

Question 7

Which formula relates concentration

Answer 7

mass / volume
mol / volume

Question 8

Which formula relates concentration

Answer 8

moles and volume?

Question 9

What is a strong acid?

Answer 9

An acid which completely splits up into its ions in water e.g. when HCl is in water all the HCl molecules split up into H+ and Cl-

Question 10

What is a weak acid?

Answer 10

An acid which will have some molecules which do not split up into their ions e.g. Ethanoic acid CH3COOH ⇌ CH3COO- + H+

Question 11

What is the relationship between the strength of an acid and its pH?

Answer 11

As an acid increases in strength

Question 12

What is a concentrated acid?

Answer 12

An acid where there are lots of acid particles in the water

Question 13

What is a dilute acid?

Answer 13

An acid where there are fewer acid particles in the water

Question 14

How does pH depend on the concentration of the H+ in a solution?

Answer 14

As the concentration of H+ increases by a factor of 10

Question 15

Define acids in terms of pH

Answer 15

A substance with a pH less than 7

Question 16

Define acids in terms of ions

Answer 16

A substance which releases H+ ions in solution

Question 17

State the three common acids and give their formulae

Answer 17

Hydrochloric acid HCl (aq)

Question 18

Which ions do the common acids form in solution?

Answer 18

HCl forms H+ and Cl-

Question 19

What is a neutral solution?

Answer 19

A solution with a pH of 7

Question 20

How do you measure pH?

Answer 20

An indicator or a pH probe

Question 21

What is a base?

Answer 21

A metal oxide

Question 22

What is an alkali?

Answer 22

A soluble base e.g. NaOH

Question 23

Which ions are always present in a solution of an alkali?

Answer 23

OH-

Question 24

What is a salt?

Answer 24

A compound formed where some or all of the hydrogen from an acid is replaced by a metal

Question 25

What is an NPK fertiliser?

Answer 25

A fertiliser with nitrogen

Question 26

How must phosphate rock be treated before it can be used as a fertiliser?

Answer 26

Reacted with acid

Question 27

What is the product of a reaction between phosphate rock and nitric, phosphoric and sulfuric acid?

Answer 27

Nitric: calcium nitrate Phosphoric: triple superphosphate (calcium phosphate) Sulfuric: single superphosphate (calcium sulfate and calcium phosphate)

Question 28

(HT) What are the two units for concentration?

Answer 28

g/dm3 and mol/dm3

Question 29

(HT) Which formula relates concentration

Answer 29

moles and volume?

Question 30

(HT) What is the purpose of titration?

Answer 30

Establish the concentration of an unknown solution

Question 31

(HT) What are concordant results?

Answer 31

Within 0.1 cm3 of each other