Chapter 5 - Chemical Changes

Question 1

What is a displacement reaction?

Answer 1

• When a more reactive metal displaces a less reactive metal from an aqueous solution.

Question 2

What is the reactivity series?

Answer 2

• A list of metal in order of reactivity, from most to least reactive.

Question 3

Define oxidation and reduction. (Hint - OIL RIG)

Answer 3

• Oxidation is a gain of electrons.
• Reduction is a loss of electrons.

Question 4

State the definition of an ore.

Answer 4

• Metals within rocks that can be extracted economically.

Include economically in your answer.

Question 5

What reaction does magnesium give when a lighted splint is present in the hydrogen produced?

Answer 5

• A squeaky ‘pop’ sounds in the presence of hydrogen.

Question 6

What is the role of hydrogen and carbon in the reactivity series?

Answer 6

• Used as reference and to see which metals can be extracted using either carbon or hydrogen.

Question 7

What is an ionic equation and what is the metal which isn’t involved in the reaction called?

Answer 7

• An equation which only shows the atoms and ions changing in a reaction.
• Spectator ions.
  (e.g 2 ions of NaOH means that NaOH would be removed from the ionic equation.)

Question 8

What are half-equations used for?

Answer 8

• To show what happens to each reactant in an equation.

Question 9

Write the ionic equation for the [displacement] of [copper (II)] ions by [iron].

Include state symbols.

Answer 9

Fe (s) + Cu2+ (aq) ———-> Fe2+ (aq) + Cu (s)

(The iron has displaced the copper oxide, leaving iron oxide and copper)

Question 10

Fe (s) + Cu2+ (aq) ———-> Fe2+ (aq) + Cu (s)

Write a half equation to show what happened to the iron during the reaction.
State whether it was reduction or oxidation.

Answer 10

Fe (s) ——–> Fe2+ (aq) + 2e-

• It gained electrons, so it was a reduction.

Question 11

Give 3 examples of metals which can be found in their native state.

Answer 11

• Gold
• Silver
• Platinum

Question 12

Give the formula for the reduction of oxides by carbon.

Answer 12

Metal Oxide + Carbon —–> Metal + Carbon Dioxide

Question 13

Define a strong acid.

Answer 13

• An acid which ionises completely. (releases H+ ions)

Question 14

Define a weak acid.

Answer 14

• An acid which partially ionises. (Don’t fully release H+ ions).

Question 15

Define the strength of an acid.

Answer 15

• How much an acid dissociates.

Question 16

Define the concentration of an acid.

Answer 16

• Amount of acid per unit of volume.

Question 17

What does a metal reacted with an acid always form?

Answer 17

• Salt + Hydrogen

Question 18

Define the reactivity of a metal.

Answer 18

• How easily it can form positive ions.

Question 19

RQP - A student wants to produce a soluble salt using some equipment and dilute HCl acid.

Describe an experiment to obtain a soluble salt. [1]

Answer 19

• Place dilute acid in beaker and heat w/ bunsen burner. [1]
• Gradually add an insoluble base. [1]
• Eventually, the base no longer disappears. It is in excess. [1]
• Filter out excess base using filter paper to obtain dissolved form of the soluble salt. [1]

Question 20

Once the dissolved salt was obtained, the student was asked to obtain pure salt crystals from the dissolved salt.

Suggest a way that he can do this.

Answer 20

• Evaporate off excess acid