[1 Mark Question Answer]

Question 11 Mark

Washing soda can be used to remove both temporary and permanent hardness in water.

Answer

Washing soda $\ce{Na_2CO_3}$ exchanges ions $\left[ SO _4\right]^{-}$and $Cl ^{-}$and do not make water hard.

Question 21 Mark

The percentage of oxygen, in air dissolved in water, is higher than the percentage of oxygen in ordinary air.

Answer

Oxygen dissolves in water and in air there are some other gases also which make the bulk of air. Some gases dissolve in water.

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Question 31 Mark

Colloidal solutions exhibit brownian movement.

Answer

Particles in colloidal solutions do not settle down and are always in motion.

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Question 41 Mark

Hardness in temporary water can be removed by boiling, but hardness in permanent hard water cannot.

Answer

Temporary hardness is due to the presence of bicarbonate of calcium or magnesium, on boiling bicarbonate decomposes to $\ce{CO_2}$, carbonate which is in soluble and can be filtered out. Where as permanent hard water contains $\left[ SO _2\right]_2-$ or $Cl ^{-}$of calcium and magnesium, cannot be removed by boiling.

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Question 51 Mark

All solutions are homogenous mixtures of a solute in a solvent.

Answer

Because solute dissapears in solvent and uniform composition throughout.

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Question 61 Mark

If $5 g$. of a solute is added to $50\ ml$. of a solvent at a particular temperature and the solution can dissolve more of the solute at that temperature $–$ is the solution obtained a saturated or an unsaturated solution. Give reasons.

Answer

As more of solute can be dissolved at that temperature, it is unsaturated solution because saturated solution cannot dissolve any more quantity of solute at a particular temperature.

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CHEMISTRY [1 Mark Question Answer]

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