Group 1

Question 1

general properties

Answer 1

alkali metals

low m.p.

soft metals

reactive to air and moisture - stored under oil

Question 2

preparation

Answer 2

Lithium and Sodium produced by electrolysis of their molten Cl- salts

2Na+ + 2e- -> 2Na
2Cl- -> Cl2 + 2e-

Question 3

oxides and hydroxides

Answer 3

all alkali metals burn in air

main product of combustion depends on metal
4Li + O2 -> 2Li2O - oxide
2Na + O2 -> Na2O2 - peroxide
K + O2 -> KO2 - superoxide (Rb and Cs react similar)

combustion in limited amount of O2 leads to intensely coloured suboxides (Rb9O2)

dissolution in H2O - hydroxides (MOH) and H2O2 (Na2O2) or O2 (KO2)

alkali metals also formed by metals in water - 2M + 2H2O -> 2MOH + H2 - violent except for Li

Question 4

chloralkali process

Answer 4

[in industry]

electrolysis of NaCl solution

2NaCl + 2H2O -> 2NaOH + H2 + Cl2

anode and cathode separated by membranes or mercury metal

Question 5

halides

Answer 5

can be prepared from hydroxides or carbonates with hydrohalic acid

Li2CO3 + 2HBr -> 2LiBr + H2O + CO2

form ionic crystal lattices - e.g. NaCl

Question 6

compounds with carbon and nitrogen

Answer 6

common binary compounds of alkali metals and carbon (carbides) based on dianion of acetylene (HC≡CH)

2Li + HC≡CH -> Li2C2 + 2H2

Li = 1 of 2 elements (Mg = other) that burns in N2

6Li + N≡N -> 2Li3N

compounds with small Li+ = stable (high lattice energy)

other salts containing oxoanions (CO3- // NO3-) are also common

Question 7

coodination chemistry

Answer 7

alkali metals are only singly charged and relatively large

binding of ligands = weaker compared to other cations

Question 8

macrocyclic polyethers

Answer 8

strong binding

selective for metal ion (size)
-too large = not fit
-too small = not all oxygens will bind

Question 9

crytands

Answer 9

greatly stabilise M+ and allow synthesis of alkalides (M-)

-crypt + 2Na -> [(crypt)Na]+Na-
-not thermodynamically stable

Question 10

alkali metals in liquid ammonia

Answer 10

gives solvated M+ and free e- - Na -> Na+ + e-

solvated e- = dark blue solution (strong reducing agent)

e- slowly reduces ammonia -> amides (NH2- ) + H2

H2O can’t react like this (too acidic + explosive)