II). Collection of Gases:
Speed of Chemical Reactions: In a chemical reaction where a gas is given off, we can measure the speed of the reaction by recording the volume of gas given off in a certain time interval, which can be measured using a gas syringe, or by recording the progressive loss in mass as the gas escapes into the air, which can be measured using a balance.
To collect a gas, the following properties may be taken into consideration:
- Its density with respect to air.
- its solubility in water
If the gas [to be collected] is denser than air, it can be collected using the downward delivery method, in which the air is displaced upward.
If the gas is lighter than air, it can be collected using the upward deliver method, in which the air is displaced downward, and the gas is collected in an upside-down container.
For gases that are insoluble or slightly soluble in water, the method of displacement of water may be used, in which the gas is passed through water into an upside down container; the gas collects on top and the water gets displaced downwards.
