An element which is preserved under water is sodium sulphur red phosphorus white

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Correct Answer

white phosphorus

Explanation

White phosphorus undergoes spontaneous combustion when exposed to air. In order to prevent this spontaneous ignition, it is preserved under water.

5. The hard Shell of an egg was dissolved in HCL. The egg was then placed in a concentration solution of NaCl. What will happens ______
Options
A. The egg will shrink
B. The egg will swell
C. The egg will become harder
D. There will be hardly any visible change

6. Heated saw dust catches fire when a drop of concentrated nitric acid is added to it. This is due to
Options
A. dehydration
B. oxidation
C. reduction
D. dehydrogenation

9. Silver Mirror test is given by which one of the following compounds? 1. Benzophenone 2. Acetaldehyde 3. Acetone 4. Formaldehyde
Options
A. Only 1
B. Only 2
C. 1 and 3
D. 2 and 4

Correct Answer: 2 and 4

Explanation:

Both Formaldehyde and Acetaldehyde will give this test

$H C H O \overset{[A g (N H_{3})_{2}^{+}]}{?} \overset{A g}{S i l v e r m i r r o r} + O r g a n i c c o m p o u n d$

$C H_{3} - C H O \overset{[A g (N H_{3})_{2}^{+}]}{?} \underset{S i l v e r m i r r o r}{A g} + O r g a n i c c o m p o u n d$

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