Which of the following statements is not correct?

• The six carbons in benzene are sp² hybridised.

• Benzene has (4n + 2) Π electrons.

• Benzene undergoes substitution reactions

• Benzene has two carbon-carbon bond lengths, 1.54 Å and 1.34 Å.

Different conformations of the same molecule are called

• isomers

• epimers

• enantiomers

• rotamers

The chlorination of ethane is an example for which type of the following reactions ?

• Nucleophilic substitution

• Electrophilic substitution

• Free radical substitution

• Rearrangement

The pair of gases responsible for acid rain are

• H₂, O₃

• CH₄, O₃

• NO₂, SO₂

• CO, CH₄

In photoelectric effect, if the energy required to overcome the attractive forces on the electron, (work functions) of Li, Na and Rb are 2.41 eV, 2.30 eV and 2.09 eV respectively, the work function of 'K could approximately be in eV.

• 2.52

• 2.20

• 2.35

• 2.01

One mole of N₂H₄ loses 10 moles of electrons to form a new compound Z. Assuming that all the nitrogens appear in the new compound, what is the oxidation state of nitrogen in Z? (There is no change in die oxidation state of hydrogen.)

• -1

• -3

• +3

• +5

Ni anode is used in the electrolytic extraction of

• Al

• Mg

• Na by Down's process

• Na by Castner's process

Which of the following is not correct?

• LiOH is a weaker base than NaOH.

• Salts of Be undergo hydrolysis

• Ca(HCO₃)₂ is soluble in water.

• Hydrolysis of beryllium carbide gives acetylene.

What is Z in the following reactions ?

$$\begin{gathered} {\mathrm{BCl}}_3+ {\mathrm{H}}_2 \underset{450°\mathrm{C}}{\overset{\mathrm{Cu}-\mathrm{Al}}{\to }} \mathrm{X} + \mathrm{HCl} \\ \mathrm{X} \stackrel{\mathrm{methylation}}{\to } \mathrm{Z} \end{gathered}$$

• (CH₃)BH₂

• (CH₃)₄B₂H₂

• (CH₃)₃B₂H₃

• (CH₃)₆B₂

20.

Which one of the following elements reduces NaOH to Na?

• Si

• Pb

• C

• Sn