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Question 22N.2.HL.TZ0.c

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Date November 2022 Marks available [Maximum mark: 3] Reference code 22N.2.HL.TZ0.c
Level HL Paper 2 Time zone TZ0
Command term Calculate Question number c Adapted from N/A
c.
[Maximum mark: 3]
22N.2.HL.TZ0.c

Polonium-210 (Po-210) decays by alpha emission into lead-206 (Pb-206).

The following data are available.

  Nuclear mass of Po-210 = 209.93676 u

  Nuclear mass of Pb-206 = 205.92945 u

Mass of the alpha particle = 4.00151 u

A sample contains 5.0 g of pure polonium-210. The decay constant of polonium-210 is 5.8 × 10−8 s−1. Lead-206 is stable.

Calculate the mass of lead-206 present in the sample after one year.

[3]

Markscheme

undecayed mass =5.0×e-5.8×10-8×365×24×60×60 «=0.8 g» ✓

mass of decayed polonium «=5.0- undecayed mass» =4.2 «g» ✓

mass of lead «=206210×4.2» =4.1 «g» ✓

 

Allow [2] max for answers that ignore mass difference between Pb and Po (4.2 g).

Allow calculations in number of particles or moles for MP1 and MP2.

Allow ECF from MP1 and MP2.

Examiners report

Several answers referred incorrectly to electron energy levels. Successful candidates managed to score full marks, although it was also common to miss the relationship between energy and wavelength.

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