PUC Science 2nd PUC Class 12 - Karnataka Board PUC Question Bank Solutions for Chemistry

Give plausible explanation for the following:

Cyclohexanone forms cyanohydrin in good yield but 2, 2, 6 trimethylcyclohexanone does not.

Give plausible explanation for the following:

There are two −NH₂ groups in semicarbazide. However, only one is involved in the formation of semicarbazones.

Complete the synthesis by giving missing starting material, reagent or product.

\[\ce{C6H5CHO ->[H2NCONHNH2]}\]

Complete the synthesis by giving missing starting material, reagent or product.

Give the equations of reactions for the preparation of phenol from cumene.

Write chemical reaction for the preparation of phenol from chlorobenzene.

You are given benzene, conc. H₂SO₄ and NaOH. Write the equations for the preparation of phenol using these reagents.

Write the equation for the preparation of 1-iodobutane from but-1-ene.

How will you bring about the following conversion?

Ethane to bromoethene

How the following conversion can be carried out?

Aniline to chlorobenzene

What happens when white phosphorus is heated with concentrated NaOH solution in an inert atmosphere of CO₂?

Write the reaction involved when D-glucose is treated with the following reagent:

Br₂ water

What happens when D-glucose is treated with the following reagent?

HI

Amongst the following compounds, identify which are insoluble, partially soluble and highly soluble in water?

1. phenol
2. toluene
3. formic acid
4. ethylene glycol
5. chloroform
6. pentanol

Give an example of the reaction in the following case.

Oxime

Give an example of the reaction in the following case.

Imine

Sucrose decomposes in acid solution to give glucose and fructose according to the first order rate law. The half life of the reaction is 3 hours. Calculate fraction of sucrose which will remain after 8 hours.

Arrange the following in increasing order of their basic strength in aqueous solution:

\[\ce{CH3NH2, (CH3)3N, (CH3)2NH}\]

For a first order reaction, show that time required for 99% completion is twice the time required for the completion of 90% of reaction.

(b) Rate constant ‘k’ of a reaction varies with temperature ‘T’ according to the equation:

`logk=logA-E_a/2.303R(1/T)`

Where E_a is the activation energy. When a graph is plotted for `logk Vs. 1/T` a straight line with a slope of −4250 K is obtained. Calculate ‘E_a’ for the reaction.(R = 8.314 JK⁻¹ mol⁻¹)