Question 53
Marcus and Arun put 20 cm³ of hydrochloric acid into each of three beakers. The acid has a pH of 1. This is like the strong acid in your stomach. They also put a few drops of universal indicator in each beaker.
They add the indigestion powder, spatula by spatula, until the acid is neutralised and the universal indicator is green. They do this with each of the three powders A, B and C. They record the number of spatulas they used.
Marcus and Arun repeat their investigation twice more. The table shows all their results.
| Powder | First try | Second try | Third try | Mean |
|---|---:|---:|---:|---:|
| A | 10 | 9 | 11 | 10 |
| B | 6 | 17 | 16 | 13 |
| C | 24 | 23 | 25 | 24 |
The values are the number of spatulas used to neutralise the acid.
Suggest why Marcus and Arun might have got this ‘wrong’ result.
They add the indigestion powder, spatula by spatula, until the acid is neutralised and the universal indicator is green. They do this with each of the three powders A, B and C. They record the number of spatulas they used.
Marcus and Arun repeat their investigation twice more. The table shows all their results.
| Powder | First try | Second try | Third try | Mean |
|---|---:|---:|---:|---:|
| A | 10 | 9 | 11 | 10 |
| B | 6 | 17 | 16 | 13 |
| C | 24 | 23 | 25 | 24 |
The values are the number of spatulas used to neutralise the acid.
Suggest why Marcus and Arun might have got this ‘wrong’ result.
