During an experiment to determine the percentage by volume of oxygen in air, a student records the following measurements:
| Measurement | Value |
|---|---|
| Volume of air in conical flask and glass tube | 210 cm3210\text{ cm}^3210 cm3 |
| Syringe reading at start | 80 cm380\text{ cm}^380 cm3 |
| Syringe reading at end | 22 cm322\text{ cm}^322 cm3 |
| Volume of oxygen reacting | 58 cm358\text{ cm}^358 cm3 |
The student incorrectly calculates the percentage by volume of oxygen in air using this working:
58×10080=72.5% \frac{58 \times 100}{80} = 72.5\% 8058×100=72.5%Identify the mistake in the student's working.
Use the values in the table to correctly calculate the percentage by volume of oxygen in air.
