DP Chemistry (last assessment 2024)

Test builder »

Question 19M.2.hl.TZ1.3f

Select a Test
Date May 2019 Marks available [Maximum mark: 2] Reference code 19M.2.hl.TZ1.3f
Level hl Paper 2 Time zone TZ1
Command term Calculate Question number f Adapted from N/A
f.
[Maximum mark: 2]
19M.2.hl.TZ1.3f

This question is about sodium and its compounds.

(f)

Sodium peroxide, Na2O2, is formed by the reaction of sodium oxide with oxygen.

2Na2O (s) + O2 (g) → 2Na2O2 (s)

Calculate the percentage yield of sodium peroxide if 5.00g of sodium oxide produces 5.50g of sodium peroxide.

[2]

Markscheme

n(Na2O2) theoretical yield «=  5.00 g 61.98 g mo l − 1 » = 0.0807/8.07 × 10−2 «mol»

OR

mass of Na2O2 theoretical yield «=  5.00 g 61.98 g mo l − 1 × 77.98 gmol−1» = 6.291 «g»    [✔]

% yield «= 5.50 g 6.291 g × 100» OR «  0.0705 0.0807 × 100» = 87.4 «%»     [✔]

 

Note: Award [2] for correct final answer.

Examiners report

The majority earned one or two marks in finding a % yield.

Syllabus sections