Group 2 exam questions

Question 1

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

Answer 1

increase in reactivity

Question 2

You are given a sample of saturated calcium hydroxide solution. Outline the
practical steps that you would take to determine the solubility of calcium hydroxide in
this solution.

Answer 2

Take a known volume of the saturated solution
Evaporate the filtrate to dryness
Weigh the residue

Question 3

State the trend in atomic radius for atoms of the elements down Group 2 from Mg to
Ba
Give a reason for this trend.

Answer 3

• increases
• due to the addition of more electron shells

Question 4

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

Answer 4

Ba(OH)2

Question 5

Strontium is extracted from strontium oxide (SrO) by heating a mixture of powdered
strontium oxide and powdered aluminium.

The use of powdered strontium oxide and powdered aluminium increases the
surface area of the reactants.
Suggest one reason why this increases the reaction rate.
Suggest one major reason why this method of extracting strontium is expensive.

Answer 5

To increase collision frequency / collisions in a given time / rate of
collisions

Reaction / process / It / the mixture requires heat

or

Aluminium is extracted by electrolysis OR aluminium extraction uses
(large amounts of) electricity

Question 6

Explain why calcium has a higher melting point than strontium.

Answer 6

(For Ca) delocalised electrons closer to cations / positive ions / atoms /
nucleus
Ca) has stronger attraction between the cations / positive ions / atoms /
nucleus and the delocalised electrons

Question 7

Write an equation for the reaction of magnesium with oxygen.
Write an equation for the reaction of magnesium with cold water.
Give a medical use for the magnesium compound formed in the reaction of
magnesium with cold water.

Answer 7

M1 2Mg + O2 —2MgO
M2 Mg + 2H2O —-Mg(OH)2 + H2
M3 Magnesium hydroxide is used as an antacid / relieve indigestion
(heartburn) / neutralise (stomach) acidity / laxative

Question 8

Give the formula of a Group 2 metal hydroxide used in agriculture.

Answer 8

Ca(OH)2

Question 9

State how barium sulfate is used in medicine.
Explain why this use is possible, given that solutions containing barium ions are
poisonous.

Answer 9

Barium meal
braium sulfate is insoluble and therefore not toxic

Question 10

Write the simplest ionic equation for the reaction that occurs when acidified
barium chloride solution is added to a solution containing sulfate ions.

Answer 10

Ba2+ + SO4 — BaSO4

Question 11

an investigation of the rate of reaction between hydrochloric acid and pure
magnesium, a student obtained the following curve.

The reaction of magnesium with dilute hydrochloric acid is exothermic.
Use your understanding of collision theory to explain why the student did not obtain
a straight line.

Answer 11

As concentration increases the amount of heat given out increases
More successful collisions or reactions in a given time OR more particles have
the activation energy
(An increase in temperature or more heat given out) increases the rate of a
reaction

Question 12

The magnesium used in a laboratory experiment was supplied as a ribbon. The
ribbon was stored in an open plastic bag exposed to the air.
Explain why it is important to clean the surface of this magnesium ribbon when
investigating the rate of its reaction with hydrochloric acid.

Answer 12

• magensium is coated with an oxide
• MgO has to be removed before the magnesium can react