Inorganic chemistry and electrochemistry

Written by Dr. Ayesha Nadeem (Chemistry)

NET · Chemistry · 6 questions

Name: ____________________ Date: ____________

Which of these has the largest atomic radius?
- A Silicon
- B Aluminium
- C Sodium
- D Magnesium
What is the oxidation number of chlorine in HClO4?
- A +5
- B -1
- C +1
- D +7
Electrolysis of concentrated sodium chloride solution (brine) gives chlorine at the anode and:
- A Sodium metal
- B Hydrochloric acid
- C Hydrogen and sodium hydroxide
- D Oxygen at the cathode
A cell reaction is spontaneous when its standard cell potential is:
- A Positive
- B Exactly 1 V
- C Zero
- D Negative
What is the electronic configuration of the Fe3+ ion? (Atomic number of iron is 26.)
- A [Ar] 3d5
- B [Ar] 3d3
- C [Ar] 4s2 3d3
- D [Ar] 3d6
How many unpaired electrons does the Mn2+ ion have? (Atomic number of manganese is 25.)
- A 3
- B 7
- C 4
- D 5

Answer key

1. C, 2. D, 3. C, 4. A, 5. A, 6. D

Atomic radius decreases across a period, so sodium, at the left of the third period, is the largest.
H is +1 and four O atoms are -8, so Cl must be +7 to make the molecule neutral.
At the cathode, water is reduced to hydrogen and hydroxide ions, which leaves sodium hydroxide in solution.
A positive E cell means a negative change in Gibbs energy, so the reaction is spontaneous.
Iron is [Ar] 4s2 3d6. It loses the two 4s electrons and one 3d electron to form Fe3+, leaving 3d5.
Mn2+ is [Ar] 3d5. The five d electrons occupy five orbitals singly, so there are five unpaired electrons.