DP Chemistry (last assessment 2024)

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Question 23M.3.HL.TZ1.4

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Date May 2023 Marks available [Maximum mark: 4] Reference code 23M.3.HL.TZ1.4
Level HL Paper 3 Time zone TZ1
Command term Explain, Sketch Question number 4 Adapted from N/A
4.
[Maximum mark: 4]
23M.3.HL.TZ1.4

Metals are often alloyed for desired characteristics.

(a)

Explain why metals alloyed with another metal are usually harder and stronger but poorer conductors than the pure metal.

[3]

Markscheme

metal ions/atoms have different sizes ✓
cations/atoms/layers do not slide over each other as easily ✓
«irregularities» obstruct free movement of electrons ✓


Accept electrons move less easily/less delocalized for M3.

(b)

Bronze is one of the oldest known alloys. Inductively coupled plasma spectroscopy can be combined with mass spectrometry (ICP–MS) or optical emission spectroscopy (ICP–OES) to analyse the structure and composition of alloys.

Sketch a typical calibration curve for ICP–OES.

[1]

Markscheme

straight line increasing and going through origin/(0,0) ✓