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Control and Coordination
A student takes about 6 ml of distilled water in each of the four test tubes P, Q, R and S. He then dissolves an equal amount of four different salts namely, sodium chloride in 'P', potassium chloride in ‘Q’, calcium chloride in ‘R’ and magnesium chloride in ‘S’. He then adds 10 drops of soap solution to each test tube and shakes its contents. The test tube in which scum (insoluble substance) is formed with soap is:
P and Q
Q and R
R and S
Q and S
A.
P and Q
C.
R and S
The correct option is C.
Scum is formed by reaction of soap with calcium and magnesium salts in water. Test tubes R and S contain calcium chloride and magnesium chloride, respectively. Therefore, scum will be formed in these two tubes.
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Take 5 ml hydrochloric acid in a boiling tube or a conical flask. Add a few pieces of zinc granules to it.
(a) What do you observe on the surface of zinc granules?
(b) Name the gas evolved.
(c) What happens when the above gas is passed through soap solution?
(d) What happens when a burning candle is brought near the gas filled tube?
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