In the hardening stage of plaster of paris, the compound formed is

• CaSO₄

• Orthorhombic CaSO₄.2H₂O

• CaSO₄.2H₂O

• Monoclinic CaSO₄.2H₂O

Sodium is heated in air at 300°C to form X. X absorbs CO₂ and forms Na₂CO₃ and Y. Which of the following is Y ?

• H₂

• O₂

• H₂O₂

• O₃

63.

In which of the following reactions, MgO is not formed?

• Mg + CO₂ →

• Mg + dil. HNO₃ →

• Mg + NO $\stackrel{∆}{\to }$

• Mg + B₂O₃

Which of the following is not correct ?

• Ammonia is used as refrigerant

• A mixture of Ca(CN)₂ and C is known as nitrolim.

• A mixture of Ca(H₂PO₄)₂ and CaSO₄ .2H₂O is known as superphosphate of lime.

• Hydrolysis of NCl₃ gives NH₃ and HOCl.

Observe the following statements:

I. Bleaching powder is used in the preparation of chloroform.

II. Bleaching powder decomposes in the presence of CoCl₃ to liberate O₃.

III. Aqueous KHF₂ is used in the preparation of fluorine.

The correct combination is :

• I, II and III are correct

• Only II is correct

• Only I and III are correct

• Only I and II are correct

Which of the following statements are correct for alkali metal compounds ?

(i) Superoxides are paramagnetic in nature.

(ii) The basic strengths of hydroxides increases down the group.

(iii) The conductivity of chlorides in their aqueous solutions decreases down the group.

(iv) The basic nature of carbonates in aqueous solutions is due to cationic hydrolysis.

• (i), (ii) and (iii) only

• (i) and (ii) only

• (ii), (iii) and (iv) only

• (iii) and (iv) only

CaOCl₂ + H₂O → Ca(OH)₂ + X

X + CH₃CHO →  Y

Y + Ca(OH)₂  → CHCl₃

 What is 'Y'?

• CH₃CH(OH)₂

• CH₂Cl₂

• CCl₃CHO

• CCl₃COCH₃

Among the following, which is water insoluble?

• Sodium fluoride

• Potassium fluoride

• Beryllium fluoride

• Magnesium fluoride

Solvay process is used in the manufacture of

• K₂CO₃

• KHCO₃

• Na₂CO₃

• CaCl₂

Assertion (A) -  K, Rb and Cs form superoxides.

Reason (R) - The stability of the superoxides increases from K to Cs due to decrease in lattice energy.

The correct answer is

• 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 not true.

• (A) is not true but (R) is true.