Group II

Question 1

What is the trend in reducing power down group II?

Answer 1

Enaught value more negative down the group
Reducing power increases down the group

Because atomic radius increase down the group, ionisation energy decreases, tendency to be oxidised is INCREASED.

Question 2

Group II ELEMENTS readily tarnish when they come into contact with air -> form metal oxide.

They are stored under l_____ p_______ with the exception of __ (protective oxide layer, tarnishes more slowly)

Answer 2

Liquid paraffin

Mg

Question 3

Colour of metal oxides’ flame:

Mg is?

Answer 3

Brilliant white

Question 4

Colour of metal oxides’ flame:

Ca is?

Answer 4

Brick red

Question 5

Colour of metal oxides’ flame:

Sr is?

Answer 5

Crimson

Question 6

Colour of metal oxides’ flame:

Ba is?

Answer 6

Apple green

Question 7

Group II ELEMENTS react with water to give metal hydroxides M(OH)2 and H2 (g).

Resulting solution is ALKALINE.

Rxn of Mg and coldwater or mg with steam?

Answer 7

Mg reacts slowly with cold water
Mg(s) + 2H2O -> Mg(OH)2 (s) + H2 (g)
(White ppt) (weakly alkaline because mgoh2 sparingly soluble, not bc it is weak base)

Reacts readily with steam
Mg (s) + H2O (g) -> MgO(s) + H2 (g)
(White residue)

PH OF 8-10

Question 8

Mg react with water pH?

Answer 8

8-10

Question 9

Ca reacts readily with cold water

Give the reaction equation and pH of resulting solution?

Answer 9

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

pH 12-14

Note how the resulting metal hydroxide is SOLUBLE

Question 10

Sr experiences VIGOROUS REACTION with cold water

Give the reaction equation and pH of resulting solution?

Answer 10

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

pH = 12-14

SOLUBLE METAL HYDROXIDE OK

Question 11

Ba undergoes vigorous reaction with cold water

Give the reaction equation and pH of resulting solution?

Answer 11

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

pH = 12-14

Question 12

Oxides of group II metals, MO are generally:

1) w____
2) i____
3) b____
4) extremely high mp (they are ionic!!!)

exception: _____ is amphoteric

Answer 12

White
Ionic
Basic

BeO

Question 13

Oxides of Group II elements react with water to form ???

MO (s) + H2O (l) -> M(OH)2 (aq)

Exception?

Answer 13

Hydroxides

BeO does not.

Question 14

Why is reaction between MgO and water slow?

Answer 14

Very exothermic lattice energy YO

Mg has higher charge density compared to the rest down the group -> higher LE

Question 15

Pattern of solubility of group II hydroxides down the group?

Answer 15

Increases down the group (think of LE decreasing down the group)

Mg(OH)2 is sparingly soluble, other hydroxides have appreciable solubilities, dissolve in water to give alkaline solutions

Question 16

Thermal decomposition of nitrates, carbonates and hydroxides

Nitrates of group 2 elements M(NO3)2 thermally unstable, decompose to give _____?

Answer 16

simple metal oxide, nitrogen dioxide (brown gas) and oxygen.

M(NO3)2(s) -> MO (s) + 2NO2 (g) + (1/2)O2(g)

Question 17

Thermal decomposition of carbonates and hydroxides are similar to that of nitrates. Equations?

Answer 17

MCO3(s) -> MO(s) + CO2 (g)

M(OH)2 (s) -> MO (s) + H2O (g)

Question 18

Why are nitrates and carbonates prone to thermal decomposition?

Answer 18

Electron clouds of large anions more susceptible to polarisation.

Oxides more thermally stable than respective metal nitrates or carbonates. (Anion O2- is relatively smaller less polarisable)

Question 19

Trend of thermal stability of nitrates down the group?

Answer 19

Increases down the group!

Radius of metal cation increases, charge density decreases. Ability of M2+ to polarise large NO32- anion decreases, N-O bonds weakened to smaller extent, so thermal stability of Group II nitrates increases down the group.

Question 20

Why are group II elements good reducing agents?

Answer 20

Standard electrode potentials all highly negative aka they are easily oxidised.

Question 21

What determines stability of carbonates nitrates down the group??

The key thing to rmb is how easily THE C,N,H are broken bc they are big anionic molecules, electron cloud easily distorted by cations (requires high charge density to polarise well and become covalent bond)

Answer 21

Down group, charge remains same but size increase, so charge density decreases.

Atomic radius of cation increase.

As charge density decrease -> polarizing power of cation decrease -> ease of distortion of electron cloud of NO3^- decrease, N-O bond less WEAKENED -> more energy required to break N-O bond -> stability increase

Question 22

Why do metal oxides have high melting point?

Answer 22

Ionic bonds, large amount of energy required to overcome strong electrostatic attraction between M2+ and O2- ions.

Question 23

BeO is actually c________ while other oxides of group 2 are ionic.

Hence it does not d_______ in water, is amphoteric, reacts with both _____________

Answer 23

Covalent
Dissolve
Acids and bases

Question 24

Why is BeO covalent?

Answer 24

Be2+ has high charge density (top of the group) so it has high polarising power, distort electron cloud of O2- a lot, become covalent. Ionic with Covalent character stuff are usually amphoteric (like Al2O3)

Question 25

Colour of group 2 metals down the group?

Answer 25

Brilliant white
Brick red
Crimson
Apple green

WRCG - where roland can’t go