INORGANIC topic 2 group 2

Question 1

This question is about Group 2 elements and their compounds

(a) Explain why the melting point of magnesium is higher than the melting point of sodium.
{2}

Answer 1

.Mg2+ has a higher charge than Na+/ Mg2+ ions are smaller /
Mg2+ has a greater charge density /
Mg atoms smaller than Na atoms /
Mg has more delocalised electrons than Na
Allow
Mg has a higher nuclear charge

.Stronger attraction to delocalised sea of electrons /
stronger metallic bonding

Question 2

State what is observed when dilute aqueous sodium hydroxide is added to separate
solutions of magnesium chloride and barium chloride. {2}

Observation with magnesium chloride :
Observation with barium chloride:

Answer 2

Observation with MgCl2: (slight) white ppt

Observation with BaCl2: no (visible) change / colourless solution / no reaction

Question 3

State and explain the trend in the first ionisation energies of the elements in Group 2 from
magnesium to barium.
Trend :
Explanation:

{3]

Answer 3

.Decrease

.Ions get bigger / more (energy) shells
Allow atoms instead of ions

.Weaker attraction of ion to lost electron

Question 4

State two observations you would make when magnesium reacts with steam. Write an
equation for the reaction.
Observation 1:
Observation 2:
Equation:

Answer 4

. white solid/ ashes
NOT PPT

.bright light

.Mg + H2O → MgO + H2

Question 5

State the trend in reactivity with water of the elements down Group 2 from Mg to Ba {1}

Answer 5

Increases / gets more reactive / reacts more vigorously / violently (down the Group)

Question 6

Give the formula of the hydroxide of the element in Group 2 from Mg to Ba that is most
soluble in water. {1}

Answer 6

Ba(OH)2

Question 7

State a medical use of barium sulfate.
State why this use of barium sulfate is safe, given that solutions containing barium ions are
poisonous.{2}
Use :
Why this use is safe:

Answer 7

. barium meal / barium swallow / barium enema
OR (used to absorb) X-rays

. it is insoluble

Question 8

Magnesium burns with a bright white light and is used in flares and fireworks.

Use your knowledge of the reactions of Group 2 metals with water to explain why water
should not be used to put out a fire in which magnesium metal is burning. {2}

Answer 8

. Hydrogen / H2 produced
OR an equation to produce hydrogen / H2
( eg Mg + 2H2O Mg(OH)2 + H2)
( eg Mg + H2O MgO + H2)

Award one mark only for ‘ exothermic reaction with steam / H2O’ for
a student who has not scored M1

.risk of explosion
OR forms explosive mixture (with air)
OR (highly) flammable