DP Chemistry (last assessment 2024)

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Question 19M.3.hl.TZ1.2b(iii)

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Date May 2019 Marks available [Maximum mark: 2] Reference code 19M.3.hl.TZ1.2b(iii)
Level hl Paper 3 Time zone TZ1
Command term State Question number b(iii) Adapted from N/A
b(iii).
[Maximum mark: 2]
19M.3.hl.TZ1.2b(iii)

Powdered zinc was reacted with 25.00 cm3 of 1.000 mol dm−3 copper(II) sulfate solution in an insulated beaker. Temperature was plotted against time.

(b(iii))

The formula q = mcΔT was used to calculate the energy released. The values used in the calculation were m = 25.00 g, c = 4.18 J g−1 K−1.

State an assumption made when using these values for m and c.

[2]

Markscheme

 

Note: Accept “copper(II) sulfate/zinc sulfate” for “solution”.

Examiners report

Explaining the assumptions made when using values for m and c was challenging in. Many referred to the accuracy of the data when using m = 25.00g or said that no mass was lost during the reaction. Most knew that the value of c used was for water and suggested that the water was pure, but did not say that the specific heat of solution was assumed to be the same as that of water.

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