Blue crystals of copper sulphate on heating in a dry test tube become colourless. Give reason.
a. Why can not a chemical change be normally reversed?
b. Why is it always essential to balance a chemical equation?
c. What happens when CO2 gas is passed through lime water and why does it disappear on
passing excess CO2?
d. Can rusting of iron take place in distilled water
Answers
Answer:
A)chemical change never reversed because it produce new substance after reaction which is not reversible . if it is reversed , it can't called chemical reaction , it called physical reaction .
B)To illustrate the chemical formulas chemical reactions of different substances, chemical equations are required.
It is important to balance the number of atoms of the reactants and products.
As per the law of conservation of mass, the mass of the products and the mass of the reactants in a chemical reaction should be equal.
When the number of the atoms on the reactants side is equal to the number of atoms on products side then we get balanced chemical equation.
C)When carbon dioxide is passed through lime water that is calcium hydroxide then calcium carbonate , insoluble white precipate and water is formed.
D)Distilled water can readily absorb oxygen from the atmosphere when compared to normal tap water. This helps in rusting.So yes, rusting of iron can take place in distilled water.
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