CBSE Class 12 Commercial Arts (Urdu) Question Paper 2018 with Answer Key (March 14)

CBSE CLASS XII Questions

• 1.

  Write mechanism of acid dehydration of ethanol to ethene.

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• 2.

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

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• 3.

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

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• 4.

  Give structures of A, B and C: $CH_3Cl \xrightarrow{KCN}$ A $\xrightarrow{LiAlH_4}$ B $\xrightarrow{CHCl_3 + \text{alc. } KOH, \Delta}$ C

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• 5.

  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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• 6.

  Why are magnesium blocks attached to iron water pipelines?

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