What happens when calcium is treated with cold water?

(i) It does not react with cold water.
(ii) Hydrogen gas evolved catches fire.
(iii) Hydrogen gas evolved does not catch fire.
(iv) Calcium floats on the surface of the water.

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Solution

Calcium doesn't undergo violent reaction with water. Though it is exothermic, the heat evolved is not sufficient for the hydrogen to catch fire.
$C a + 2 H_{2} O \to C a (O H)_{2} + H_{2}$
Calcium starts floating because the bubbles of hydrogen gas formed during the reaction stick to its surface and lift it up.

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Similar questions

What happens when calcium is treated with water?

(i) It does not react with water.
(ii) It reacts violently with water.
(iii) It reacts less violently with water.
(iv) Bubbles of hydrogen gas formed stick to the surface of calcium.

(a) Name a metal for each case:

(i) it does not react with cold as well as hot water but reacts with steam.

(ii) It does not react with any physical state of water.

(b) When calcium metal is added to water, the gas evolved does not catch fire but the same gas evolved on adding sodium metal to water catches fire. Why is it so?

Question 6
What happens when calcium is treated with water?

(i) It does not react with water.
(ii) It reacts violently with water.
(iii) It reacts less violently with water.
(iv) Bubbles of hydrogen gas formed stick to the surface of calcium.

a) (i) and (iv) (b) (ii) and (iii)

Q. Assertion :Calcium floats over water during the reaction with water. Reason: Calcium reacts with water less vigorously so that the heat evolved is not sufficient for the hydrogen formed, to catch fire. The bubbles of hydrogen gas formed stick to the surface of the water calcium

Q. Statement I:- Hydrogen gas is not evolved when zinc reacts with cold water.

Statement II:- Sodium reacts vigorously with cold water to produce sodium hydroxide and hydrogen gas.

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What happens when calcium is treated with cold water? (i) It does not react with cold water. (ii) Hydrogen gas evolved catches fire. (iii) Hydrogen gas evolved does not catch fire. (iv) Calcium floats on the surface of the water.

Calcium doesn't undergo violent reaction with water. Though it is exothermic, the heat evolved is not sufficient for the hydrogen to catch fire. Ca + 2H2O → Ca(OH)2 + H2 Calcium starts floating because the bubbles of hydrogen gas formed during the reaction stick to its surface and lift it up.

What happens when calcium is treated with cold water?

(i) It does not react with cold water.
(ii) Hydrogen gas evolved catches fire.
(iii) Hydrogen gas evolved does not catch fire.
(iv) Calcium floats on the surface of the water.