31.

Hardest compound of boron is

• magnesium boride

• aluminium boride

• boron nitride

• boron carbide

Rate determining step in nitration of benzene is

• formation of NO₂⁺

• formation of carbocation

• replacement of H atom

• none of these.

The aqueous solution of which of the following salt will have the lowest pH ?

• NaClO₃

• NaClO

• NaClO₄

• NaClO₂

Which ofthe following alkanes is optically active?

• 3-Methylhexane

• Propane

• 2, 3, 4-Trimethylpentane

• 2-Methylbutane

Assertion : Na₂SO₄ is soluble in water while BaSO₄ is not.

Reason : Lattice energy of BaSO₄ exceeds its hydration energy.

• If both Assertion and Reason are true and Reason is the correct explanation of Assertion.

• If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.

• If Assertion is true but Reason is false.

• If Assertion is false but Reason is true.

Which of the following is soluble in water?

• Br

• Sr

• Mg

• Ba

Which azide is explosive?

• Ba(N₃)₂

• NaN₃

• KN₃

• Mg₃N₂

Strongest acid among the following is

• acetic acid

• FCH₂COOH

• F₂CHCOOH

• F₃CCOOH

Which of the following hydrogen halides is most  basic?

• HF

• HCl

• HBr

• HI

Which of the following has highest second  ionization energy?

• Ni

• V

• Cr

• Mn