A-Level Chemistry Fundamentals

Question 1

What is the shape and bond angle of a methane (CH₄) molecule?

Accepted Answer

Tetrahedral, 109.5°

Answer

Methane has four bonding pairs of electrons around the central carbon atom with no lone pairs, giving a tetrahedral shape with bond angles of 109.5° as predicted by VSEPR theory.

Question 2

Which of the following best describes an ionic bond?

Accepted Answer

Electrostatic attraction between oppositely charged ions formed by electron transfer

Answer

Ionic bonding involves the transfer of electrons from a metal to a non-metal, creating positively and negatively charged ions held together by strong electrostatic attraction in a giant ionic lattice.

Question 3

In a titration, 25.0 cm³ of 0.100 mol dm⁻³ NaOH is exactly neutralised by HCl. If 20.0 cm³ of HCl was used, what is its concentration?

Accepted Answer

0.125 mol dm⁻³

Answer

Moles of NaOH = 0.025 × 0.100 = 0.0025 mol. NaOH:HCl ratio is 1:1, so moles of HCl = 0.0025. Concentration = 0.0025 / 0.020 = 0.125 mol dm⁻³.

Question 4

What is the oxidation state of manganese in the permanganate ion MnO₄⁻?

Accepted Answer

+7

Answer

Each oxygen is -2, giving 4 × (-2) = -8. The overall charge is -1. So Mn + (-8) = -1, therefore Mn = +7. Permanganate is a powerful oxidising agent due to this high oxidation state.

Question 5

Which of the following molecules exhibits hydrogen bonding?

Accepted Answer

HF

Answer

Hydrogen bonding requires hydrogen bonded to a highly electronegative atom (F, O, or N). HF fits this criterion as fluorine is the most electronegative element. H₂S and PH₃ only have weaker van der Waals forces as S and P are not sufficiently electronegative.

A-Level Revision Practice Test

A-Level Revision Practice Test

A-Level Chemistry Fundamentals