Questions

Question 1

Describe the structure and bonding in magnesium.

Answer 1

M1 (giant) lattice of (Mg2+) cations / (giant) lattice of (Mg) atoms

M2 (Electrostatic) attractions between cations delocalised electrons

Question 2

M is a Group 2 metal that forms the nitrate M(NO3)2
0.320 g of M(NO3)2 is heated strongly and decomposes completely.
2 M(NO3)2(s) → 2 MO(s) + 4NO2 (g) + O2 (g)
The mixture of gases formed has a volume of 225 cm3 at 450 °C and 101 000Pa
Determine the Mr of M(NO3)2
Identify M.
The gas constant, R = 8.31 J K–1 mol –1

Answer 2

M1 V = 225×10–6 m3 ; T = 723 K
M2
n = pV
RT
=
101 000 × 225 × 10−6
8.31 × 723 = 3.78 × 10–3 mol
M3
n = M2 ×
2
5
= 1.51 × 10–3 mol
M4
Mr = mass
mol =
0.320
( M3) = 211.9
M5
Ar (M) = 211.9 – 124.0 = 87.9, so
M is Sr

You multioly by 2/5 bevcause there are 5 moles of gas and youve got two moles of that solid

Question 3

Explain why the electronegativity of the halogens decreases down the group

Answer 3

M1 Larger atoms / more electron shells / more shielding / bonding pair
of electrons further from the nucleus
M2
weaker attraction between nucleus and bonding pair of electrons /
weaker attraction between nucleus and shared pair of electrons /
weaker attraction between nucleus and electron density in the
covalent bond