4.1 3 Reactions Of The Group 2 Oxides And Hydroxides

Question 1

Group 2 oxides

Answer 1

Basic oxides can react with water to form alkalis . Only observation is the solids react to form colorless solutions
General equation :
MO(s)+H2O(l)=M(OH)2(aq)
Or O2-+H2O=2OH- (why the resulting solutions are alkaline )

Question 2

pH value of the alkaline solution

Answer 2

Relative amounts of oxide and water but also different solubility of hydroxides
Solubility increases down the group
Maximum pH also increases down group

Question 3

Testing for carbon dioxide

Answer 3

Limewater goes cloudy as a precipitate forms . Lime water is saturated aqueous solution of calcium hydroxide
CO2+Ca(OH)2=CaCO3+H2O

Question 4

Milk of magnesia

Answer 4

Saturated solution of magnesium hydroxide mixed with extra solid magnesium hydroxide
Indigestion remedy
Mg(OH)2+2HCl=MgCl2+2H2O
Neutralizes some of the hydrochloric acid in the stomach
OH- at too low conc to cause damage

Question 5

Group 2 oxides and hydroxide react with acids

Answer 5

Form salts and water neutralization reactions
White solid reacts to form a colorless solution
Endothermic
E.g MgO+H2SO4=MgSO4 +H2O
Ba(OH)2+2HCl=BaCl2+2H2O

Question 6

Use in agriculture

Answer 6

Lime mostly calcium hydroxide and neutralizes excess acidity in the soil nitric acid represents acid in the soil.
Ca(OH)2+2HNO3=Ca(NO3)2 +2H2O

Question 7

Trends in the solubility of Group 2 sulfates

Answer 7

All group 2 nitrates and chlorides are soluble but group 2 sulfates solubility decrease down the group
Magnesium sulfate = soluble
Calcium sulfate = slightly soluble
Strontium sulfate and barium sulfate are insoluble

Question 8

Testing for sulfate ions

Answer 8

Adding a solution containing barium ions (usually barium chloride or barium nitrate) form a white precipitate of barium sulfate
Ba2+(aq)+SO42-(aq)=BaSO4(s)
Low solubility of barium sulfate used

Question 9

Barium ions

Answer 9

Other anions could also form a white precipitate especially carbonate ions H+ ions prevent barium carbonate forming a white precipitate therefore dilute nitric acid or dilute hydrochloric acid is added to test
Ba(NO3)2(aq)+Na2SO4(aq)=BaSO4(s)+2NaNO3(aq)

Question 10

Barium metals

Answer 10

Barium sulfate used in hospitals not poisonous because they are insoluble . Barium ions not free to move soft tissues show up more clearly because of the dense white solid