S block

Question 1

How does the energy of orbitals change going down the group?

Answer 1

Down the group orbitals decrease in energy as they increase in size.

Question 2

How is most H2 formed

Answer 2

Heating natural gas or light crude oil fractions with steam, high temp, Ni catalyst,  
eg 
CH4+H2OCO + 3H2
CO + H2O CO2 + H2
(Fe catalyst second reaction)

Question 3

What is another way to produce H2 What are the pro and con of this reaction

Answer 3

Electrolysis of H2O
2H2O -> 2H2 + O2
Con: Is expensive so best where the electricity of cheap
Pro: Produces H2 without producing green house gas CO2

Question 4

What are the uses of H2

Answer 4

1) Production of ammonia
2) production of methanol (CO + 2H2 CH3OH)
3) hydrogenation of saturated compounds in the chemical industry.

Question 5

What are the classes of compounds formed by Hydrogen

Answer 5

1) Covalent hydrides - individual discrete molecules formed usually with p-block elements
2) Saline hydrides - ionic hydrides
3) Metallic hydrides

Question 6

Explain the trend of E-H bonds down the group

Answer 6

Down the group, E-H bond becomes less stable due to valence orbitals become larger and more diffuse and so worse overlap.

Question 7

Explain the trend of E-H bonds across a period

Answer 7

More stable going L to R across rows due to better overlap between orbitals and increase in ionic character

Question 8

How does MP change down group 1 metals

Answer 8

Decreases down the group and increasing s orbital size down group resulting in less overlap and weaker bonds

Question 9

How are Li and Na metals obtained

Answer 9

Via electrolysis of their molten chlorides:

2NaCl -> 2Na + Cl2

Question 10

How are K Rb Cs metals obtained

Answer 10

Reduction of their molten salts with Na at high temps:

KCl + Na -> NaCl + K

Question 11

State the reactions of G1 metals with water, H2 and X2

Answer 11

M + H20 -> MOH + 0.5H2
2M + H2 -> 2MH
2M + X2 -> 2MX

Question 12

How do metal hydrides react with water

Answer 12

Violently

MH + H2O -> MOH + H2

Question 13

When burnt in the air what G1 metals give what type of oxo anion

Answer 13

Li gives Oxide O^2-
Na peroxide O2 ^2-
K(+heavier) Superoxide O2^-

Question 14

How do sizes of oxo-anions trend

Answer 14

O2- < O2 - < O2 2-

Question 15

What are the trends for the solubility of group 1 salts

Answer 15

most G1 salts are soluble in water
Salts with large anions - solubility decreases down group
Small anions - solubility increases down the group

Question 16

predict the solubility for the combos: 
Small cation + small anion
Small cation + large anion
Large cation + small anion
Large cation + large anion

Answer 16

insoluble
soluble
soluble
insoluble

Question 17

How does reactivity trend down G2

Answer 17

Increases gown the group due to decreasing IE and decreasing lattice enthalpies

Question 18

How does MTP differ down G2

Answer 18

Decreases down the group but not a regular decrease due to the different metallic structures

Question 19

How is Mg manufactured on large scale, what are the main uses of Mg

Answer 19

Thermally decomposing metal carbonates:
1) MgCO3.CaCO3 -> MgO.CaO + 2CO2
2) 2MgO.CaO + Si -> Mg + Ca2SiO3
used in aluminium alloys, Mg gives greater mechanical strength and resistance to corrosion

Question 20

What are the properties and the uses of Be

Answer 20

One of the lightest metals known, non-magnetic and high thermal conductivity / melting point, used in satellites, nuclear reactors and Beryllium alloys

Question 21

How does G2 react with air

how does Mg and Be differ

how does the rest of G2 react with water

Answer 21

Burns in air to give metal oxide
Mg and Be are passivated and kinetically inert to O2 and H2O forming protective oxide coating on the metal surface

Forms metal hydroxide and hydrogen gas
M + 2H2O -> M(OH)2 + H2

Question 22

How does G2 react with N2, sulphur and halogens

Answer 22

sulphur: 8M + S8 -> 8MS
3M + N2 -> M3N2
M + X2 -> MX2

Question 23

What makes Be form covalent compounds

Answer 23

Be2+ has very high charge density and therefore polarises all anions and ligands giving polar-covalent compounds

Question 24

In Aq solution what coordinate do Be2+, Mg2+ and Ca2+ form

Answer 24

Be: Always 4
Mg: 4, but usually 6
Ca: 6 or 8