pmt q

Question 1

State what is observed when dilute aqueous sodium hydroxide is added to
separate solutions of magnesium chloride and barium chloride.

Answer 1

Observation with MgCl2: (slight) white ppt
1
Observation with BaCl2: no (visible) change / colourless solution / no
reaction

Question 2

This question is about Group 2 elements and their compounds.
(a) Explain why the melting point of magnesium is higher than the melting
point of sodium.

Answer 2

Mg2+ has a higher charge than Na+ / Mg2+ ions are smaller / Mg2+ has a
greater charge density / Mg atoms smaller than Na atoms / Mg has more
delocalised electrons than Na

Stronger attraction to delocalised sea of electrons / stronger metallic
bonding

Question 3

Chlorine has a low boiling point because the forces between the molecules
are weak.
Explain how these forces arise between molecules of chlorine

Answer 3

(Random) movement of electrons in one molecule (creates a dipole) /
a (temporary) dipole is formed in one molecule / an imbalance in
electron density in one molecule
1
Induces a dipole in a neighbouring molecule.
1
(These) temporary dipoles attract / temporary attraction between δ+ and δ–

Question 4

Give an equation for the reaction of chlorine with water.
Give a reason why chlorine is added to drinking wate

Answer 4

Cl2 + H2O ⇌ HCl + HClO / 2 Cl2 + 2 H2O → 4 HCl + O2
Kills bacteria

Question 5

Chlorine reacts with cold, aqueous sodium hydroxide in the manufacture of
bleach.
Give an equation for this reaction.

Answer 5

Cl2 + 2 NaOH → NaCl + NaClO + H2O