Group 2 metals

Question 1

Give the equation for Ca reacting with water

Answer 1

Ca(s) + 2H2O(l) —> H2(g) + Ca(OH)2 (aq)

Question 2

What test can be used to see if Hydrogen is present?

Answer 2

The gas is collected and a lit splint placed inside, hydrogen is present if a squeaky pop is heard

Question 3

Why does hydrogen cause a squeaky pop?

Answer 3

The reaction is very exothermic and causes the glass to ring

Question 4

What is the pH of aqueous Calcium hydroxide?

Answer 4

11

Question 5

What is the pH of aqueous barium hydroxide?

Answer 5

13

Question 6

Describe what would be seen in the reaction between Ca and water

Answer 6

• Grey solid reaction with a colourless liquid to form a colourless liquid with a white precipitate
• Metal sinks to the bottom and disappears
• effervescence

Question 7

Give the reaction for Magnesium and oxygen

Answer 7

2Mg(s) + O2(g) —> 2MgO(s)

Question 8

Give the reaction for Magnesium and hydrochloric acid

Answer 8

Mg(s) + 2HCl(aq) —> MgCl2 (aq) + H2(g)

Question 9

What is the trend in reactivity for reactions of group 2 metals?

Answer 9

Reactivity increases

Question 10

Why does reactivity increase down the group?

Answer 10

• Group 2 metals react by losing electrons
• the no. electron shells increases so more shielding occurs
• this results in an increase in atomic radius
• therefore there is a weaker electrostatic attraction between the nucleus and outershell electrons
• electrons are lost more easily

Question 11

What is the trend in solubility of group 2 metal hydroxides?

Answer 11

Solubility increases down the group

Question 12

How soluble are group 2 metal oxides in water?

Answer 12

Partially soluble

Question 13

Give the equation for the reaction between calcium oxide and water

Answer 13

CaO(s) + H2O(l) —> Ca2+ (aq) + 2OH-(aq)

Question 14

Why does the solubility of metal hydroxides increase down the group?

Answer 14

• metal IONS get bigger down the group
• as ions get bigger, charge intensity gets smaller
• so it is easier to break apart the ions
• so it is easier to dissolve the compounds

Question 15

Why does the pH of metal hydroxide solutions increase down the group?

Answer 15

• alkalinity increases
• because metal hydroxides get more soluble
• the concentration of OH- ions increases

Question 16

Give a use for calcium hydroxide

Answer 16

-used to increase pH of acidic soils

Question 17

Give a use for magnesium hydroxide solution

Answer 17

-used as a treatment for heartburn/acid reflux

Question 18

Why is the 3rd ionisation energy for calcium much greater than the 1st and 2nd ionisation energies?

Answer 18

• electron is being taken from the next electron shell
• this experiences less shielding as it is closer to the nucleus
• therefore nuclear attraction is greater

Question 19

Under what condition does Magnesium react with water?

Answer 19

When the water is steam

Question 20

Define solubility

Answer 20

A measure of the ability of a solute to dissolve in a solvent

Question 21

Define alkalinity

Answer 21

A measure of the concentration of hydroxide ions present in an alkaline solution

Question 22

How could you measure the solubility of group 2 metal carbonates in water?

Answer 22

• Add to carbonates drop by drop until a precipitate appears

- Count how many drops were needed