Alkali metals-Andreas Stasch

Question 1

Define electronegativity

Answer 1

The dimensionless ability of an atom to attract electrons in a chemical bond.

Question 2

What is the relationship between electron gain energy and electron affinity?

Answer 2

Ege=-Ea

Question 3

Explain the general trend in atomic radii

Answer 3

Decreases across a period, increases down a group

Question 4

Explain general properties of metals

Answer 4

Low Ei, low x, high melting point, conductive,malleable

Question 5

Explain general properties of alkali metals

Answer 5

White low density metals that are highly reactive and strong reducing agents.

Question 6

Explain the trends in group 1 for Ei, mp, bp, Esub

Answer 6

All are lowest of the periodic table and decrease down the group.

Question 7

2NaCl(l) +(conditions)–>2Na(l)+Cl2(g).

What are the conditions? What is this process called?

Answer 7

Molten sodium chloride at around 600C(CaCl2 added to lower mp) and electrolysis occurring with 4-8V.
This is called the Downs process.

Question 8

Na(l) + KCl(l)–>NaCl(l)+K(g)

This is surprising considering their reduction potentials, why does this occur then?

Answer 8

It’s lower bp and larger lattice energy of NaCl drives this forward, only if it occurs at high T and K is removed.

Question 9

4NaPb+4EtCl–>?

Answer 9

PbEt4+3Pb+4NaCl

Question 10

4Li+O2–>1
2Na+O2–>2
K+O2–>3
What is the relation between them?

Answer 10

1. 2Li2O (O2-)
2. Na2O2 (O2 2- peroxide)
3. KO2(O2 - radical)

Question 11

4KO2+6H2O–>?

Answer 11

4K+ + 4OH- + 3O2

Question 12

6Li+N2–>2Li3N

Why does Li react with N2 but others do not?

Answer 12

The small cation can activate the triple bond, and forms a stable lattice with the N3- ion.

Question 13

2M+2H2O –>2MOH+H2

The heavier metals react more violently, why?

Answer 13

As they melt under the heat so form a fresh reactive surface.

Question 14

Na/K is liquid at room temperature, what else is a unique feature?

Answer 14

Good thermal conductivity, used in power plants and can dry solvents.

Question 15

What happens when the metals react with graphite?

Answer 15

They reduce the carbon layers and form intercalation compounds in which they are bonded between the graphite layers. i.e KC8

Question 16

LiC6–>?
CoO2+Li+ + e- –>?
what are the products fort these equations in a Li-ion battery?

Answer 16

Li+ + C6 + e-

LiCoO2

Question 17

M2CO3/2MOH + 2HX –>?

Answer 17

2MX+2H2O (+CO2)

Question 18

2M+H2–>2MH
Why does this form as an ionic lattice, and what is the trend for reactivity?
2MH+H2O–> 2M(OH)+H2

Answer 18

As there is a big mismatch between the electronegativity values for H and M, with LiH being the least reactive, as to a greater matching ionic radii.

Question 19

True/false, M2+ oxoanions are more soluble in water than M+?

Answer 19

False

Question 20

Are LI+ lattices soluble in ethereal solvents?

Answer 20

Yes if there is a big difference in electronegativity.

Question 21

Explain how hydrogen bonds arise in a hydrated M+ complex.

Answer 21

In the first solvation sphere, the molecules are bonded directly to the M+ cation. However, in the second solvation sphere, due to weak interactions between the M+ cation and the outer molecules, they are bonded by hydrogen bonds to the first solvation sphere.

Question 22

When M+ metals react with dry ammonia, electrides form, what is the formula and simplified formula for these?

Answer 22

M+ +(NH3)n+m –> M(NH3)n+ + e(NH3)m

Question 23

What metal can an M- alkalide not be?

How is the M- alkalide formed?

Answer 23

Li

Disproportionation

Question 24

nBuCl+(2n)Li –> ?

Answer 24

nBuLi + nLiCl

Question 25

What is the use of nBuLi?

Answer 25

Used as an organometallic solvent, strong base, strong nucleophile and a polymerisation starter.