S-Block Chemistry

Question 1

Group 1 favourite oxidation state:

Answer 1

Group 1 is dominated by the +1 oxidation state, so are really good reducing agents, as they try to lose an electron

Question 2

Lithium burns in oxygen, show the equation:

Answer 2

4Li (s) + O2 (g) -> 2Li2O (s)

Question 3

Sodium burns in oxygen, show the equation:

Answer 3

2Na (s) + O2 (g) -> Na2O2 (s)
produces sodium peroxide, peroxide ion is larger, charge is spread out across 2 molecules,

Question 4

Potassium burns in oxygen, show the equation:

Answer 4

K (s) + O2 (g) -> KO2 (s)
produces a superoxide, size is likely bigger than the peroxide ion, as it has a bigger mass to charge ration
oxidation state of K in KO2 = +1, O = -0.5

Question 5

What oxides do group 1 make if they are heavier than potassium?

Answer 5

Superoxides, because larger ions make larger oxides

Question 6

Hydroxide formation equation from sodium:

Answer 6

2Na (s) + 2H2O (l) -> 2NaOH (aq) + H2 (g)

Question 7

Hydroxide formation equation from sodium peroxide:

Answer 7

Na2O2 (s) + H2O (l) -> 2NaOH (aq) + 1/2O2 (g)

Question 8

Group 1 hydroxide reaction trend

Answer 8

Reactions are increasing exothermic down the group -> heat ignites the hydrogen produced

Question 9

The reaction of group 1 metals with water creates vigorous reactions. Explain why rubidium and caesium reactions are dangerous

Answer 9

2Rb (s) + 2H2O (l) -> 2RbOH (aq) + H2 (g)
(1) reaction is extremely exothermic which ignites the H2, which creates a risk of explosion.

Question 10

Most important group 1 Halide:

Answer 10

NaCl (Soduim chloride)

Question 11

Lithium halide formation equation:

Answer 11

Li2CO3 (s) + 2HCl (aq) -> 2LiCl (aq) + CO3^2- + 2H+

Question 12

Lithium carbonate decomposition equation:

Answer 12

Li2CO3 (s) -> Li2O (s) + CO2 (g)

Question 13

Write a chemicale equation for the decomposition of lithium carbonate under heat. Explain why sodium carbonate doesn’t decompose in the same way.

Answer 13

Li2CO3 (s) -> Li2O (s) + CO2 (g) [under heat conditions - add delta above arrow]
Sodium preferentially forms Na2O2 because the m/c ratio stabilises the peroxide ion:
Na2CO3 (s) -> Na2O2 (s) + CO (g) [under heat conditions - add delta above arrow]
[indicative of the reaction, may not be correct equation]

Question 14

Group 2 favourite oxidation state:

Answer 14

Group 2 is dominated by the +2 oxidation state, so are really good reducing agents, as they try to lose an electron

Question 15

Group 2 oxides formula

Answer 15

Generally: 2M (s) + O2 (g) -> 2MO (s)
Heavier metals (e.g Barium): 2BaO (s) + O2 (g) -> BaO2 (s)

Question 16

Hydroxide formation equation from Barium:

Answer 16

Ba (s) + 2H2O (l) -> Ba(OH)2 (aq) + H2 (g)

Question 17

Hydroxide formation equation from oxides:

Answer 17

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

Question 18

Hydroxide reaction with CO2:

Answer 18

Ca(OH)2 (aq) + CO2 (g) -> CaCO3 (s) + H2O (l)

Question 19

Halide formation from Mg:

Answer 19

Mg (s) + Cl2 (g) -> MgCl2 (g)

Question 20

Does Beryllium form a halide?

Answer 20

No, beryllium doesn’t form ionic species