Suggested experiments
1. Conduct an experiment to observe the speed of diffusion of two substances
Answers
Answer:
In the experiment to study diffusion using hydrogen chloride (HCl) gas and ammonia (NH4Cl), the experiment is conducted as follows:
The required apparatus are:
2 Cotton buds
A test tube
2 Glass stoppers
Ammonia solution
Hydrogen Chloride acid
Procedure for the experiment:
Soak 1 cotton bud into ammonia solution and fix on one end of the testube.
Soak the other cotton wool on concentrated hydrochloric acid and fix on the other end of the test tube.
Use the glass stoppers to close both ends of the test tubes.
The results of the experiment:
In the test tube, the two gases will diffuse towards each other.
When the two gases meet inside the test tube they react with one another and form a ring of Ammonium chloride that is white in color.
The ring is formed closer to the end where hydrogen chloride is. This is because hydrogen chloride gas is heavier and diffuses slower than ammonium chloride.
This experiment is used to test the rate of diffusion of gases and the speed at which they diffuse.
EXTRA INFORMATIOn
Diffusion of Gas in Gas:
Experiment:
One gas jar is filled with CO2 (either by laboratory method: CaCO3 + HCL, or by allowing living plant tissue to respire in a closed jar). Another jar is similarly filled with O2 (either by laboratory method: Mono + KClO2, or by allowing green plant tissue to photosynthesize in a dosed jar). The gases may be tested with glowing match stick.
The oxygen jar is then inverted over the mouth of the carbon dioxide jar and made air-tight with grease. It is then allowed to remain for some time. The jars are carefully removed and tested with glowing match stick.
Observation:
The glowing match sticks flared up in both the jars.
Inference:
The diffusion of CO2 and O2 takes place in both the jars until finally the concentrations are same in both of them making a mixture of CO2 and O2. Hence the glowing match sticks flared up in both the jars.
Experiment # 4
Comparative Rates of Diffusion of Different Solutes:
Experiment:
3.2gm of agar-agar is completely dissolved in 200 ml of boiling water and when partially cooled, 30 drops of methyl red solution and a little of 0.1 N NaOH are added to give an alkaline yellow colour. 3 test tubes are filled three-fourth full with agar mixture and allowed to set.
The agar is covered with 4 ml portion of the following solutions, stoppered tightly and kept in a cool place:
(a) 4 ml of 0-4% methylene blue,
(b) 4 ml of 0.05 N HCl, and (4.2 ml of 0.1ml HCL plus 2 ml of 0-4% methylene blue.
The diffusion of various solutes is recorded in millimeters after 4 hours. The top of the gel should be marked before the above solutions are added.
Observation:
The rate of diffusion of HCL alone (tube b) is faster compared to the combination of methylene blue and HCl (tube c) and minimum in case of methylene blue alone (tube a).
Inference:
Different substances like gases, liquids and solutes can diffuse simultaneously and independently at different rates in the same place without interfering each other.
HCL being gaseous in nature and of lower molecular weight can diffuse much faster than methylene blue which is a dye of higher molecular weight having an adsorptive property. Hence in combination, these; two substances diffuse more readily than methylene blue alone.
