Reactions of the Group 2 oxides and hydroxides, and trends in solubility

Question 1

group 2 oxides are classed as

Answer 1

basic oxides

Question 2

basic oxide are

Answer 2

oxides of metals that react with water to form metal hydroxides, and with acids to form salts and water

Question 3

the reaction of a group 2 metal oxide with water has what observations?

Answer 3

that the white solids react to form a colourless solution

Question 4

the general equation for the reactions of group 2 metal oxides and water is

Answer 4

Mo(s) + H2O(l) = M(OH)2(aq)

Question 5

the ionic equation for the reaction of group 2 oxide with water is

Answer 5

O2- + H2O = 2OH-

Question 6

the resulting solution formed by the reaction of group 2 oxides and water is (acid or alkaline)

Answer 6

alkaline, as OH- ions are formed

Question 7

the trend in the solubility of group 2 hydroxides is

Answer 7

an increase in solubility down the group

Question 8

the poor solubility of magnesium hydroxide means that the solution formed when the magnesium oxide reacts with water is not very

Answer 8

alkaline

Question 9

as the solubility of the group 2 hydroxides increases down the group, this also means the ……..increases

Answer 9

the pH as the hydroxide is alkaline, so if more of it dissolves, the pH increases down the group

Question 10

limewater is the names used to mean

Answer 10

a saturated aqueous solution of calcium hydroxide

Question 11

limewater is used to test for

Answer 11

carbon dioxide

Question 12

when carbon dioxide reacts with limewater, the equation is

Answer 12

CO2 + Ca(OH)2 = CaCO3 + H2O

Question 13

milk of magnesia is a name used for

Answer 13

a saturated solution of magnesium hydroxide mixed with extra solid magnesium hydroxide, which acts as an antacid

Question 14

the equation for the reaction of milk of magnesia with hydrochloric acid is

Answer 14

Mg(OH)2 + 2HCl = MgCl2 + 2H2O

Question 15

milk of magnesia is safe to use for humans even though hydroxide ions attack tissue because

Answer 15

the magnesium’s low solubility means that the concentration of OH- ions in the medicine is also very low

Question 16

all of the group 2 oxides and hydroxides react with acids to form

Answer 16

salts and water

Question 17

during the reactions of group 2 oxides and hydroxides with an acid, the only observations are

Answer 17

• that a white solid reacts to form a colourless solution
• the reactions are exothermic so an energy change can be measured (if uT - vT is used, the energy reading will be positive)

Question 18

lime is

Answer 18

mostly calcium hydroxide, obtained from limestone, calcium carbonate