21.

Assertion : The position of an element in periodic table after emission of one α and two β-particles remains unchanged.

Reason : Emission of one α and two β-particles give isotope of the element which acquires same position in periodic table.

• 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 both assertion and reason are false.

Which of the following radioisotopes is used as anticancerous?

• Na-24

• C-14

• U-235

• Co-60

The repeating unit in silicone is

• SiO₂

• R₂Si-O^-

• 

• 

Propene on hydroboration and oxidation produces

• CH₃CH₂CH₂OH

• CH₃CHOHCH₃

• CH₃CHOHCH₂OH

• CH₃CH₂CHO

Among the following components of cement which is present in highest amount?

• Ca₂SiO₄

• Ca₃SiO₅

• Al₂O₃

• Ca₃Al₂O₆

Which of the following species participate in sulphonation of benzene ring?

• H₂SO₄

• SO₃

• HSO${}_3^{-}$

• SO${}_2^{-}$

Assertion : trans-butene on reaction with bromine forms racemic mixture.

Reason : trans-compound in trans addition forms two types of stereoisomers.

• 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 both assertion and reason are false.

Assertion : The lactic acid shows the geometrical isomerism.

Reason : Lactic acid has carbon-carbon double bond.

• 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 both assertion and reason are false.

The coordination number in hcp is

• 6

• 12

• 18

• 24

Cyanogen gas is obtained in the reaction

• CuSO_4 (aq) + KCN $\to$

• K₄[Fe(CN)₆] $\stackrel{\mathrm{heat}}{\to }$

• CH₃CN + H₂O $\stackrel{∆}{\to }$

• CH₃CONH₂ + P₂O₅ $\stackrel{∆}{\to }$