Re: some tys qns to clarify -- Chemistry

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Date Posted: 05:19:12 11/04/01 Sun
Author: Mr. Yeo Woei Ter
Subject: Re: some tys qns to clarify
In reply to: Eugenia 's message, "some tys qns to clarify" on 05:54:58 11/03/01 Sat

Hi Eugenia!

1) I suppose you are referring to page (1)3, Question 11.
The answer provided, A, is correct.
This question is talking about a dilute sugar solution. Therefore the molecules of sugar are widely separated and moving at random. Particles in a solution are moving and not stationery. The solvent in this solution is water. Thus, there are lots of water molecules in it. They are close together and moving at random (refer to the movement and arrangemnet of particles in the liquid state).

2) The answer, B, is correct. Particles in the gaseous state are moving randomly and throughout the balloon. So option B gives a better diagram which represents the mixture of helium and argon.
If you have a mixture of air and helium, then the diagram will be a little more complicated as you have to draw the particles of nitrogen gas, oxygen gas, argon, carbon dioxide as well as small amount of other noble gases!

3) No we cannot! We have to bubble the gas into liquid Y. To do this, the tube where gas X enters must be immersed into liquid Y.

4) I'm just about to type the question here. The correct answer is C. When we are heating a solid strongly, there is a chance that the solid in the crucible will jump out. We do not want this to happen in this experiment as we need to measure the mass of magnesium oxide formed at the end accurately (refer to Page 107 of "*textbook!" Experiment 6.1).

5) If we heat it directly using the Bunsen burner, the hydrated crystals will lose it's water of crystallisation easily. We want to obtain dry CuSO₄.5H₂O. So we cannot do that!
By placing the dish under direct sunlight, the crstals will not lose it's water of crystallisation as the temperature will not go up to 90 degree celsius. By doing so, we allow the crsytals to dry slowly without losing its water of crystallisation.

Hope you understand.

P.S.: Can you help me to e-mail the rest to come here to look at the discussion, especially the mistakes I pointed out in your TYS? I tried to mass e-mail those in my contact list, but some mails bounced back!!! Help me to let those without interner access to know about it as well!

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