DP Chemistry (first assessment 2025)

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Question 19M.1A.SL.TZ1.27

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Date May 2019 Marks available [Maximum mark: 1] Reference code 19M.1A.SL.TZ1.27
Level SL Paper 1A Time zone TZ1
Command term Question number 27 Adapted from N/A
27.
[Maximum mark: 1]
19M.1A.SL.TZ1.27

Which has the strongest conjugate base?

A. HCOOH (Ka = 1.8 × 10−4)

B. HNO2 (Ka = 7.2 × 10−4)

C. HCN (Ka = 6.2 × 10−10)

D. HIO3 (Ka = 1.7 × 10−1)

[1]

Markscheme

C

Examiners report

Strength of conjugate bases appeared to be another good discriminator, with higher scoring candidates performing better.

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