Chemistry
Assertion (A): Hard water does not form lather with soap easily.
Reason (R): Temporary hardness can be removed by boiling.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
Answer
Both A and R are true but R is not the correct explanation of A.
Explanation — Hard water contains dissolved calcium and magnesium salts. These ions react with soap to form an insoluble scum, therefore lather is not produced easily. So, Assertion (A) is true.
Temporary hardness (due to bicarbonates of Ca and Mg) can be removed by boiling. So, Reason (R) is true.
However, Reason (R) is not the correct explanation of Assertion (A) because it tells a method of removing temporary hardness, not the reason for poor lather formation.
Therefore, both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
Related Questions
Assertion (A): A solution is a heterogeneous mixture of two or more substances with variable composition.
Reason (R): The component of a solution that dissolves is called as solute, while the other component in which the solute dissolves is called a solvent.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
Assertion (A): Pure water is tasteless but the water which we drink has taste.
Reason (R): Drinking water contains dissolved minerals and gases.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
Fill in the blanks:
(a) Water has ………………… density and …………….. volume at 4°C.
(b) Freezing mixture contains ……………… and ……………. .
(c) The solubility of a gas in water …………….. with rise in temperature and ………………….. with rise in pressure.
(d) ………………. is the purest form of natural water.
(e) Use of excessive ……………… by farmers causes water pollution.
(f) Boiling removes the ………………. hardness of water.
(g) Water turns the colour of anhydrous copper sulphate ………………. .
(h) The sticky substance formed when soap is added to hard water is …………………. .
Write true or false for the following statements and correct the false ones.
(a) Hard water forms lather easily with soap.
(b) Permanent hardness is due to bicarbonate salts of calcium and magnesium.
(c) Silica gel is a drying agent.
(d) The reaction of steam with magnesium produces hydrogen gas and magnesium hydroxide.
(e) An example of a colloid is ink.