Edexcel IAL Chemistry A2 6.P4 evaluate results and conclusions

This question is about the nitration of methyl benzoate.

The equation for the reaction is shown.

Procedure

Step 1 Weigh between 1.9 g and 2.1 g of methyl benzoate in a $50 \mathrm{~cm}^{3}$ conical flask.
Step 2 Slowly add $5 \mathrm{~cm}^{3}$ of concentrated sulfuric acid to the methyl benzoate with swirling and place the flask in an ice-water bath to cool.

Step 3 Place $2.0 \mathrm{~cm}^{3}$ of concentrated nitric acid into a test tube.
Cool the nitric acid by immersing the test tube in an ice-water bath before slowly adding $2.0 \mathrm{~cm}^{3}$ of concentrated sulfuric acid.
Allow this nitrating mixture to cool.
Step 4 Using a teat pipette, add the nitrating mixture very slowly to the conical flask, ensuring the temperature does not exceed $7^{\circ} \mathrm{C}$.

Step 5 Allow the flask to stand at room temperature for about 15 minutes and then pour the contents into a beaker containing some crushed ice. Impure methyl 3-nitrobenzoate will form.

Step 6 Recrystallise the methyl 3-nitrobenzoate using methanol as the solvent.
Step 7 Weigh the dry crystals and determine their melting temperature.

1.95 g of methyl benzoate reacted with an excess of nitric acid to form
1.51 g of methyl 3-nitrobenzoate.
[Molar mass values: methyl benzoate, $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CO}_{2} \mathrm{CH}_{3}=136 \mathrm{~g} \mathrm{~mol}^{-1}$
methyl 3-nitrobenzoate, $\mathrm{C}_{6} \mathrm{H}_{4} \mathrm{CO}_{2} \mathrm{CH}_{3} \mathrm{NO}_{2}=181 \mathrm{~g} \mathrm{~mol}^{-1}$ ]

Give one possible reason why the yield in (d)(i) is less than 100\%.