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It consists of three cases followed by questions. There are a total of 12 questions (Q. No. 49 to 60 ) in this section. Attempt any 10 questions from this section. The first attempted 10 questions would be evaluated. P-Did not react eiter with cold or hot water but reacted with steam
Q- Reacted with hot water and the metal started floating
R - Reacted violently with cold water
S- Did not react with water at all
Based on the above observation answer the following:
Case-I:
A student, took four metalsP , Q , R
- All metal could not be cut with knife except metal R.
- Metal P combined with oxygen to form an oxideM 2 O 3
- Reaction with water.
Q- Reacted with hot water and the metal started floating
R - Reacted violently with cold water
S- Did not react with water at all
Based on the above observation answer the following:
Case-I:
A student, took four metals
- All metal could not be cut with knife except metal R.
- Metal P combined with oxygen to form an oxide
- Reaction with water.
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Question : 50
Total: 60
Out of the given metals, the metal Q
Solution:
Magnesium is a very reactive metal. It reacts with hot water and forms magnesium hydroxide and hydrogen gas. Magnesium hydroxide being insoluble in water deposits on the surface of the magnesium metal and cuts off the contact of magnesium with water and the reaction stops. Hydrogen gas bubbles formed on the surface of the magnesium metal makes it lighter than water. Hence, magnesium metal floats on water.
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