Some students design an experiment to investigate the effect of sucrose concentration on the rate of anaerobic respiration in yeast. The apparatus collected carbon dioxide gas over water in a measuring cylinder.
Method:
Some of the results are shown in the tables below:
Table 1: Results for 4%4\%4% sucrose
| Time (s) | Trial 1 (cm3\text{cm}^3cm3) | Trial 2 (cm3\text{cm}^3cm3) | Trial 3 (cm3\text{cm}^3cm3) | Mean (cm3\text{cm}^3cm3) | Standard deviation |
|---|---|---|---|---|---|
| 30 | 6 | 6 | 7 | 6.3 | 0.6 |
| 60 | 11 | 12 | 11 | 11.3 | 0.6 |
| 90 | 16 | 17 | 15 | 16.0 | 1.0 |
| 120 | 20 | 21 | 19 | 20.0 | 1.0 |
Table 2: Results for 20%20\%20% sucrose
| Time (s) | Trial 1 (cm3\text{cm}^3cm3) | Trial 2 (cm3\text{cm}^3cm3) | Trial 3 (cm3\text{cm}^3cm3) | Mean (cm3\text{cm}^3cm3) | Standard deviation |
|---|---|---|---|---|---|
| 30 | 38 | 35 | 38 | 37.0 | 1.7 |
| 60 | 62 | 59 | 62 | 61.0 | [ To be calculated ] |
| 90 | 74 | 70 | 72 | 72.0 | 2.0 |
| 120 | 81 | 75 | 78 | 78.0 | 3.0 |
(i) State the independent variable in this investigation.
(ii) Describe how a student could produce a 12%12\%12% dilute sucrose solution from the 20%20\%20% stock solution.
(i) Calculate the standard deviation for the 60 s60\text{ s}60 s result at 20%20\%20% sucrose. Use the formula:
s=∑(x−xˉ)2n−1 s = \sqrt{\frac{\sum(x - \bar{x})^2}{n - 1}} s=n−1∑(x−xˉ)2Give your answer to 1 decimal place.
(ii) Calculate the initial rate of reaction over the first 30 s30\text{ s}30 s for the result at 4%4\%4% sucrose. Include the appropriate unit.
