Class 11th

9.44. Choose the incorrect statement:

(a) H⁺ can exist freely.

(b) Hydrogen combines with other elements by losing, gaining, or sharing of electrons.

(c) Hydrogen forms electrovalent and covalent bonds with other elements.

(d) H⁺ isextremely small as compared to normal atomic and ionic sizes of 50 to 200 pm.

9.43. Choose the incorrect statement:

(a) Hard water is not suitable for laundry.

(b) Temporary hardness can be removed by boiling.

(c) Calgon is used for removing permanent hardness of water.

(d) Calgon forms precipitates with Ca²⁺ and Mg²⁺.

MCQs:

9.42. Hydrogen peroxide in the name of perhydrolis used as

(a) Antipyretic

(b) Antiseptic

(c) Analgesic

(d) All of the above

9.41. Assertion: Hard water is desirable for laundry.

Reason: Soap containing sodium stearate (C₁₇H₃₅COONa) reacts with hard water to precipitate out Ca/Mg stearate.

9.40. Assertion: An ice cube floats on water. 

Reason: Density of ice is more than that of water.

9.39. Assertion: Lithium hydride used in the synthesis of other useful hydrides.

Reason: Lithium hydride is very reactive at moderate temperatures with O₂ or Cl₂.

9.38. Assertion: H⁺ does not exist freely and is always associated with other atoms or molecules.

Reason: H⁺ form hydrides.

Assertion and Reason:

Directions:

(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.

(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.

(c) Assertion is correct statement but reason is wrong statement.

(d) Assertion is wrong statement but reason is correct statement.

9.37. Assertion: H₂O₂ is stored in wax-lined glass or plastic vessels in dark.

Reason: H₂O₂ decomposes slowly on exposure to light.

9.36. What do you understand by the terms:

(i) Hydrogen economy 

(ii) Hydrogenation

(iii) Syngas

(iv) Water-gas shift reaction

(v) Fuel-cell?

9.35. How does H₂O₂ behave as a bleaching agent?