C3

Question 1

What colour is methyl orange in acid, neutral and alkali?

Answer 1

Acid: red
Neutral: peachy yellow
Alkali: yellow

Question 2

What colour does blue litmus paper turn in acid, alkali and neutral?

Answer 2

Acid: red
Neutral: blue
Alkali: blue

Question 3

What colour does red litmus paper turn in acid, alkali and neutral?

Answer 3

Acid: red
Neutral: red
Alkali: blue

Question 4

If the pH decreases by one unit, what happens to the concentration of hydrogen ions?

Answer 4

Hydrogen concentration increases by a factor of 10

Question 5

What is a base?

Answer 5

Ant substance that reacts with water to form salt and water only

Question 6

Why are metal oxides normally bases rather than alkalis?

Answer 6

• metal oxides are normally insoluble
• alkalis are soluble

Question 7

What method would be used to prepare a soluble salt from an acid and insoluble reactant?

Answer 7

• adding excess of the soluble reactant
• it will be fully reacted, however excess can still be removed via filtration

Question 8

What method would be used to prepare a soluble salt from an acid and soluble reactant?

Answer 8

• titration
• as they are both soluble, it allows the exact amount to be added, whilst making sure everything reacts

Question 9

Are chlorides soluble or insoluble?

Answer 9

• soluble
• except for silver chloride and lead chloride, which are insoluble

Question 10

Are nitrates soluble or insoluble?

Answer 10

• all soluble

Question 11

Are common sodium, potassium and ammonium salts soluble or insoluble?

Answer 11

• all soluble

Question 12

Are sulfates soluble or insoluble?

Answer 12

• most soluble
• lead sulfate, calcium sulfate and barium sulfate are insoluble

Question 13

Are common carbonates and hydroxides soluble or insoluble?

Answer 13

• most insoluble
• except sodium, potassium and ammonium which are soluble

Question 14

How could you prepare a pure, dry sample of an insoluble salt?

Answer 14

• mix two substances together to form salt
• filter
• residue is the insoluble salt
• wash and leave to dry

Question 15

What is a precipitate and how do you know if it is formed when forming a salt?

Answer 15

• a precipitate is an insoluble product that forms when two solutions are mixed and react together
• you can tell this from the rules of solubility

Question 16

Why can an electrolyte carry charge?

Answer 16

As when molten, there are mobile ions which carry charge

Question 17

Name the processes that occur at each electrode

Answer 17

Anode (positive) oxidation: loss of electrons to the anions to form non-metal
Cathode (negative) reduction: gain of electrons to the cations to form metal or hydrogen

Question 18

How can you predict whether a metal or hydrogen will form at the negative electrode?

Answer 18

• if hydrogen is more reactive than the metal, the metal will form
• if hydrogen is less reactive than the metal, the hydrogen will form

Question 19

What is the format (half equation) of an oxidation reaction?

Answer 19

Fe²⁺ -> Fe³⁺ + e⁻

Question 20

What is the format (half equation) of a reduction reaction?

Answer 20

Fe³⁺ + e⁻ -> Fe²⁺

Question 21

What is the formula for sulphuric acid?

Answer 21

H₂SO₄

Question 22

What is the formula for nitric acid?

Answer 22

HNO₃

Question 23

What is the formula for sodium hydroxide?

Answer 23

NaOH