A student investigated the rate of the reaction between zinc and sulfuric acid. The equation for the reaction is: Zn(s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g). Figure 10 shows the apparatus.
The method used is:

1. Pour 50 cm³ of sulfuric acid into the conical flask.
2. Add excess zinc to the conical flask.
3. Insert the stopper and start a timer.
4. Measure the volume of hydrogen collected in the 50 cm³ measuring cylinder every 20 seconds for 180 seconds.

Explain why the volume of hydrogen collected in the 50 cm³ measuring cylinder is less than the volume of hydrogen produced.

There are several potential sources of error in this experimental setup that would lead to the collected volume of gas being less than the actual volume produced by the chemical reaction. 1. **Gas lost at the start:** The reaction between zinc and sulfuric acid starts immediately upon contact. There is a delay between adding the zinc (step 2) and inserting the stopper (step 3). During this time, hydrogen gas is being produced and escaping from the open neck of the conical flask into the room, so it is not collected. 2. **Solubility of gas:** Hydrogen is only slightly soluble in water, but some of the gas produced will dissolve in the water in the trough and measuring cylinder instead of displacing it. This dissolved gas is not measured as part of the collected volume. 3. **Leaks:** If the stopper is not a tight fit, or if there are any other leaks in the apparatus (e.g., around the delivery tube), some gas could escape instead of being channelled into the measuring cylinder.