1)
Observe the figure and answer the following questions-
a) What happens when the clamp is removed?
b) Does the water stop flowing? Why?
c) What will you do to keep the water flowing for a longer duration?
Answers
Answer:
Condenser Hoses
The condenser is an intricate piece of glassware, and allows for cold water to circulate through the distillation apparatus. The circulating water does not mix with the sample to be purified, but instead passes through another jacket surrounding the hollow tube where the gaseous sample travels. It is important that the water jacket be full of cold water, to maximize the efficiency of condensing the gaseous sample. It is for this reason that the water hoses must be attached to the condenser in a certain way.
A hose should connect from the water spigot to the lower arm of the condenser, forcing water to travel against gravity through the condenser (this is shown correctly in Figure 5.17b). The hose connecting the upper arm of the condenser should then drain to the sink. By forcing the water uphill, it will completely fill the condenser. The hoses are connected incorrectly in Figure 5.17a, with water flowing into the upper arm of the condenser. With a downhill flow of water, only the lower portion of the condenser fills with the circulating water, leading to inefficient cooling of gas traveling through the inner tube.
Figure 5.17: a) Condenser hoses connected incorrectly: notice that water does not fill the condenser's jacket (as indicated with the small arrow), b) Condenser hoses connected correctly.
Whether the condenser hoses point up or down seems to be a personal choice, as there are pros and cons to both orientations. When the hoses point downward, there is a small portion of the condenser that does not fill with cooling water (Figure 5.18a), but the effect is likely minimal. When the hoses point upwards, there is sometimes a tendency for the hoses to bend and pop off, spraying water all over the lab (this can sometimes be avoided by securing wire around the hose joints). Personal judgment may be applied to whether the condenser hoses point up or down.
Figure 5.18: a) Condenser hoses pointed downward:notice the small pocket where water does not circulate, b) Hoses upwards.
Simple Distillation Procedure
An assembled simple distillation apparatus is shown in Figure 5.19. Assembly of this complicated apparatus is shown in this section piece by piece. The glassware used for this apparatus is quite expensive, and undoubtedly your instructor would appreciate care being taken when using this experiment. A single condenser costs $72, and a complete kit containing all the glassware needed for distillation costs $550! 88
Distillation apparatus with thermometer adapter, three-way adapter, distilling flask, heating mantle, condenser, vacuum adapter, receiving flask
Figure 5.19: Simple distillation apparatus.
Figure 5.20: Organic chemistry students perform distillation.
The answers to the questions are given below:
a) When the clamp is removed, the water starts flowing from the bottle at the higher altitude to the bottle at the lower altitude through the pipe attached to them.
b) Yes, after some time the water flow will stop. This happens when the water level in both the bottles is equal i.e. there is no difference in the height of the water levels.
c) To keep the water flowing for a longer duration, the water level difference should be maintained. This can be done by constantly pouring water into the bottle at a higher altitude.
(The image of the question is attached below.)
