Potassium sulfate contains K⁺ and SO₄^2- ions - AQA - GCSE Chemistry Combined Science - Question 2 - 2022 - Paper 1

According to Figure 2, the volume of hydrogen collected is 30 cm³ and the volume of oxygen collected is 15 cm³.

The volumes of hydrogen and oxygen collected are in a 2:1 ratio, which reflects the molecular ratio of hydrogen to oxygen in water (H₂O). This supports the student's hypothesis, as 2 volumes of hydrogen are produced for every 1 volume of oxygen during electrolysis.

The measure of uncertainty in the 4 experiments is 9 ± 1 cm³, as the range of measurements (from 6 cm³ to 11 cm³) gives a mean of 9 cm³ with a deviation of 1 cm³.

Given that 0.86 g of potassium sulfate is dissolved in 25 cm³, the concentration can be calculated as follows:

1. Convert 25 cm³ to dm³:

   $25 ext{ cm}^3 = 0.025 ext{ dm}^3$

2. Calculate concentration:

   ext{Concentration} = rac{0.86 ext{ g}}{0.025 ext{ dm}^3} = 34.4 ext{ g/dm}^3

3. For 1.0 dm³ of solution:

   $ext{Mass} = 34.4 ext{ g/dm}^3 imes 1.0 ext{ dm}^3 = 34.4 ext{ g}$.