Science (English Medium) कक्षा १२ - CBSE Important Questions

Write the structures of the following molecule: 

H₂SO₃

Give reasons for the following : H₂Te is the strongest reducing agent amongst all the hydrides of Group 16 elements.

Write the structures of the main products when acetone (CH₃ − CO − CH₃) reacts with the following reagents :

CH₃MgBr and then H₃O⁺

Draw the structures of the following:
(1) HClO₄
(2) H₃PO₃

Complete the following equation: 

\[\ce{XeF2 + H2O ->}\]

Give reasons Fluoride ion has higher hydration enthalpy than chloride ion.

Give reason for the following:

Red phosphorus is less reactive than white phosphorus.

Arrange the following in order of the property indicated set.
HF, HCl, HBr, HI - decreasing bond enthalpy.

Write the mechanism of the following reaction : 

\[\ce{C2H5OH->[H2SO4][443K]CH2=CH2 + H2O}\]

Account for the following : 
t-butyl chloride on heating with sodium methoxide gives 2-methylpropene instead of t-butyl methyl ether.

Answer the following question.
Write the disproportionation reaction of H₃PO₃. 

Draw the structure of XeF₄. 

Account for the following : 
Although Fluorine has less negative electron gain enthalpy yet F₂ is a strong oxidizing agent.

Answer the following question.
Write a chemical reaction to test sulphur dioxide gas. write a chemical equation involved.

Give a simple chemical test to distinguish between the following pair of compounds:

Ethanal and Propanal

A compound 'A' of molecular formula C₂H₃OCl undergoes a series of reactions as shown below. Write the structures of A, B, C and D in the following reactions :

Distinguish between the following : Benzoic acid and methyl benzoate

Write the structure of 2-methylbutanal.

Write the structures of the main products when acetone (CH₃ − CO − CH₃) reacts with the following reagent :

Zn − Hg/conc. HCl

Write the structures of the main products when acetone (CH₃ − CO − CH₃) reacts with the following reagent :

H₂N − NHCONH₂/H⁺