AQA A-Level Chemistry Paper 3, 2023: Question 8

1 mark · Easy difficulty · Multiple Choice

Relative Molecular Mass of Benzene-1,4-Dicarboxylic Acid This question involves calculating the Mr (relative molecular mass) of benzene-1,4-dicarboxylic acid using the atomic masses of its constituent element

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Question

AQA A-Level Chemistry Paper 3, 2023: Question 8
Question text

08 What is the relative molecular mass (Mr) of benzene-1,4-dicarboxylic acid?

[1 mark]

A 164.0

B 166.0

C 168.0

D 170.0

Mark scheme

Show the mark scheme Mark scheme for AQA A-Level Chemistry Paper 3, 2023: Question 8

08 B 1 (AO2) 166.0

How to answer it

Step-by-Step Guide: Calculating Mr of Benzene-1,4-Dicarboxylic Acid

Step 1: Determine the Molecular Formula

Benzene-1,4-dicarboxylic acid has the molecular formula: C8H6O4 .

Teacher Tip: The name "dicarboxylic acid" indicates two carboxyl (-COOH) groups attached to the benzene ring.

Step 2: Calculate the Relative Atomic Mass (Ar) of Each Element

Use the periodic table to find the Ar:

  • Ar of Carbon (C) = 12.0
  • Ar of Hydrogen (H) = 1.0
  • Ar of Oxygen (O) = 16.0

Step 3: Multiply Each Ar by the Number of Atoms

For the molecular formula C8H6O4:

  • Carbon: 12.0 × 8 = 96.0
  • Hydrogen: 1.0 × 6 = 6.0
  • Oxygen: 16.0 × 4 = 64.0

Step 4: Add the Values to Get the Mr

Mr = 96.0 + 6.0 + 64.0 = 166.0

Teacher Tip: Ensure all numbers are added correctly. Check your work twice to avoid errors!

Final Answer

The relative molecular mass (Mr) of benzene-1,4-dicarboxylic acid is:

166.0

The correct answer is B.

Topics

Physical Chemistry · 3.1.2 Amount of Substance

Question and mark scheme from the AQA A-Level Chemistry examination, Paper 3, 2023. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.