group 2 - alkaline earth metals

Question 1

what are the elements of group 2

Answer 1

-beryllium
-magnesium
-calcium
-strontium
-barium
-radium

Question 2

what happens to atomic radius down the group

Answer 2

increase - greater distance bwt nucleus and outer electrons there are a greater number of full outer shells as there are more electrons as u go down group

Question 3

what happens to first ionisation energy

Answer 3

decreases
- larger atomic radius so more shielding
- weaker attraction bwt nucleus and outer electrons so less energy to remove one mole of electrons from gaseous atom

Question 4

what happens to the melting and boiling points

Answer 4

general decrease
weaker metallic bonding down group
atom gets larger so there is a weaker attraction bwt +ve ion and delocalised electrons

Question 5

group 2 reactions of metal and water

Answer 5

magnesium- slow reaction with a small amount of gas produced and indicator turns blue
Mg(s) + 2H20(l) = Mg(OH)2 (aq) + H2
calcium - vigorous fizz and white precipitate forms
Ca + 2H2O = Ca(OH)2 + H2
Barium- very vigorous fizzing + white precipitate forms
same equation just with Ba

Question 6

reaction of magnesium with steam

Answer 6

glows white flame and produces a white precipitate
Mg + H2O(g)= MgO + H2
this happens bc the magnesium hydroxide that is formed in the first part of reaction breaks off and form magnesium oxide and hydrogen gas

Question 7

how does the reactivity change

Answer 7

increases

Question 8

why does the reactivity increase

Answer 8

-metals react and they lose their 2 outer shell electrons down group
-atomic radius increases and have more shielding
-weaker attraction bwt nucleus and outer shell so electrons are more easily lost making the metal more reactive

Question 9

what is the trend in group 2 sulfates solubility down the group

Answer 9

they get less soluble - more insoluble and more precipitate can be seen

Question 10

what is the trend for group 2 hydroxides solubility down the group

Answer 10

get more soluble less insoluble - less ppt

Question 11

what is an explanation for the hydroxides alkalinity

Answer 11

Going down the group, the solutions formed from the reaction of group 2 oxides with water become more alkaline
When the oxides are dissolved in water, the following ionic reaction takes place:
O2- (aq) + H2O (l) → 2OH- (aq)

The higher the concentration of OH- ions formed, the more alkaline the solution
The alkalinity of the solution formed can therefore be explained by the solubility of the Group 2 hydroxides

Question 12

what are the reactions of group 2 with water

Answer 12

The reaction of all metals with water follows the following general equation:
M (s) + 2H2O (l) → M(OH)2 (s) + H2 (g)

Except for, Be which does not react with water
speed of reactions increase - get more vigorous down group

Question 13

what are the reactions of group 2 with oxygen

Answer 13

The reaction of group 2 metals with oxygen follows the following general equation:
2M (s) + O2 (g) → 2MO (s)

Where M is any metal in group 2

Remember than Sr and Ba also form a peroxide, MO2
get more difficult to ignite going down group

Question 14

what are the reactions of group 2 with acid

Answer 14

The Group 2 metals will react with dilute acids to form colourless solutions of metal salts
For example, they will form colourless solutions of metal chlorides if reacted with hydrochloric acid
When metals react with an acid, the by-product of this reaction is hydrogen gas
When some of Group 2 metals react with sulfuric acid rather than hydrochloric, an insoluble sulfate forms
Going down the group, the Group 2 sulfates become less and less soluble
Calcium sulfate is sparingly soluble, but strontium sulfate and barium sulfate are insoluble
The reaction of the metals with dilute HCl follows the following general equation:
M (s) + 2HCl (aq) → MCl2 (aq) + H2 (g)

The reaction of the metals with dilute H2SO4 follows the following general equation:
M (s) + H2SO4 (aq) → MSO4 (aq) + H2 (g)

Remember that SrSO4 and BaSO4 are insoluble

Question 15

what are the uses of group 2

Answer 15

-extraction of titanium - using reduction of magnesium
- magnesium hydroxide in medicine- used as a laxative for constipation, used as an antacid to treat heartburn + indigestion and to treat lime and seawater
-calcium hydroxide in agriculture- slaked lime - neutralise acidic soil to encourage growth of plants
-use of barium sulphate in medicine - used in x-rays as it is opaque soo xrays dont pass through soft tissue- eat barium sulphate in a meal which would then be absorbed into tissues
-CaO or CaCO3 to remove SO2 from flue gas
- acidified barium chloride can test for sulphate ions - white ppt upon acidify with HCl andthen add Ba2Cl2

Question 16

reactions of group 2 metal oxide and acid

Answer 16

Group 2 sulfates also form when a group 2 oxide is reacted with sulfuric acid
The insoluble sulfates form at the surface of the oxide, which means that the solid oxide beneath it can’t react with the acid
This can be prevented to an extent by using the oxide in powder form and stirring, in which case neutralisation can take place
Remember that:
metal oxide + dilute hydrochloric acid → metal chloride + water

metal oxide + dilute sulfuric acid → metal sulfate + water

Question 17

recations of group 2 carbonates

Answer 17

ll group 2 carbonates (except for BeCO3) are insoluble in water
All group 2 carbonates will form soluble chloride salts, water and carbon dioxide gas when reacted with dilute hydrochloric acid
The carbonates of Ca, Sr and Ba form as an insoluble sulfate layer on their solid carbonates which stops any further reaction after the initial bubbling (effervescence) of carbon dioxide gas is seen

carbonate + dilute hydrochloric acid → chloride + water + carbon dioxide

carbonate + dilute sulfuric acid → sulfate + water + carbon dioxide

Question 18

reactions of group 2 hydroxides

Answer 18

The group 2 metal hydroxides form colourless solutions of metal salts when they react with a dilute acid
The sulfates decrease in solubility going down the group (barium sulfate is an insoluble white precipitate)

hydroxide + dilute hydrochloric acid → chloride + water

hydroxide + dilute sulfuric acid → sulfate + water

Question 19

observations of the reactions of group 2 with oxygen

Answer 19

Mg- Burns easily + Bright white light
Ca- Difficult to ignite + Red flame
Sr- Difficult to ignite + Red flame
Ba- Difficult to ignite + Green flame

Question 20

observations of group 2 with water

Answer 20

Mg -Vigorous reaction with steam, no reaction with water
Ca-Reacts moderately, forms a hydroxide
Sr-Reacts rapidly, forms a hydroxide
Ba-Reacts rapidly, forms a hydroxide

Question 21

observations with dilute HCl

Answer 21

all react vigorously

Question 22

observations with dilute sulphuric

Answer 22

Mg-Vigorous reaction with steam, no reaction with water
Ca-Reaction slowed by the formation of a sparingly soluble sulfate layer on the metal, stopping hydrogen bubbles from rising
Sr-Reaction is quickly stopped by the formation of an insoluble sulfate layer on the metal
Ba-Reaction is quickly stopped by the formation of an insoluble sulfate layer on the metal