CBSE Class 12 Biology Ophthalmic Question Paper 2018 with Answer Key

CBSE CLASS XII Questions

• 1.

  Though chlorine shows strong $-I$ effect, why is it ortho/para directing?

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• 2.

  For decomposition of $H_2O_2$ by $I^-$: Step I: $H_2O_2 + I^- \rightarrow H_2O + IO^-$ (slow). Step II: $H_2O_2 + IO^- \rightarrow H_2O + I^- + O_2$ (fast). (a) Write rate law. (b) Determine order w.r.t. $H_2O_2$ and $I^-$ and overall order. (c) Molecularity of Step II.

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• 3.

  Give structures of A, B and C: Aniline $\xrightarrow{Br_2/H_2O}$ A $\xrightarrow{NaNO_2+HCl, 0-5^\circ C}$ B $\xrightarrow{H_3PO_2+H_2O}$ C

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• 4.

  Which isomer of $C_4H_9Br$ is most reactive towards $S_N1$ reaction?

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• 5.

  Explain: (i) Presence of carbonyl group in glucose. (ii) Presence of five $-$OH groups attached to different carbon atoms.

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• 6.

  Predict the alkene formed by dehydrohalogenation of 1-Bromo-1-methylcyclohexane.

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