Chemistry
Give reasons for the following:
All solutions are homogenous mixtures of a solute in a solvent.
Hardness in temporary water can be removed by boiling, but hardness in permanent hard water cannot.
Colloidal solutions exhibit brownian movement.
The percentage of oxygen, in air dissolved in water, is higher than the percentage oxygen in ordinary air.
Washing soda can be used to remove both temporary and permanent hardness in water.
Water
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Answer
As solute dissolves in the solvent and forms a uniform composition throughout hence, all solutions are homogenous mixtures of a solute in a solvent.
On boiling, the calcium and magnesium bicarbonates responsible for temporary hardness in water, decompose into insoluble carbonates and carbon dioxide which are filtered out making water soft.
The chlorides and sulphates of calcium and magnesium responsible for permanent hardness in water, are stable to heat hence, permanent hardness cannot be removed by boiling.Colloidal solutions exhibit Brownian movement due to the constant bombardment of molecules of the dispersion medium on the colloidal particles.
Ordinary air contains 21% oxygen. As oxygen is more soluble in water as compared to air. Hence, air in water contains 33% oxygen which is more than that in ordinary air.
On adding washing soda to water containing calcium & magnesium chlorides, sulphates & bicarbonates an insoluble precipitate of calcium & magnesium carbonate is formed which is filtered out. The remaining soln. contains soluble sodium salts which do not cause hardness in water & hence the residual water is rendered soft. Hence, washing soda can be used to remove both temporary and permanent hardness in water.
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Related Questions
Select the correct answer from A, B, C, D & E for each statement given below:
A: Colloidal
B: Fused calcium chloride
C: Solvent
D: Suspension
E: Washing soda
The medium of dissolution which allows the solute to dissolve in it.
A solution which can pass through a filter paper but not through a semipermeable membrane
A monohydrate crystal.
A drying agent placed in desiccator.
A heterogenous mixture of undissolved particles in dispersion medium, visible to the naked eye.
Give a balanced equation for the following conversions:
Calcium sulphate in permanent hard water to calcium carbonate using sodium carbonate
Iron to triiron tetroxide using steam.
Sulphur dioxide to sulphurous acid using a neutral liquid.
Potassium oxide to a strong alkali.
Magnesium bicarbonate in temporary hard water to magnesium carbonate by boiling.
Complete the statements by filling the blanks with the correct word from the bracket.
Solubility of most solids …………… (decreases/increases) with rise in temperature.
Kerosene & water form a …………… (miscible/immiscible) mixture.
Solubility of a solute is the …………… [minimum/maximum] amount of solute that will saturate 100 g. of water at t°C.
Hygroscopic substance absorb moisture from the atmosphere & …………… (do not change/change) their original state.
The ratio of hydrogen & oxygen in water is …………… (2:1/1:2)
Match the substances in List I with the appropriate answer in List II.
List List II 1. Green vitriol A: Permanent hardness in water 2. Paint B: Hygroscopic 3. Magnesium chloride C: Temporary hardness in water 4. Magnesium bicarbonate D: Heptahydrate 5. Calcium oxide E: Colloidal