Science (English Medium) इयत्ता १२ - CBSE Important Questions for Chemistry

Write the product(s) in the following reactions: 

Which would undergo S_N2 reaction faster in the following pair and why ?

CH₃ – CH₂ ​– Br and CH₃ ​– CH₂ ​– I

Indicate the principle behind the method used for the refining of Nickel.

What is the role of dilute NaCN in the extraction of gold ?

What is 'copper matte' ?

An element X (molar mass = 60 g mol⁻¹) has a density of 6.23 g cm⁻³. Identify the type of cubic unit cell, if the edge length of the unit cell is 4 ✕ 10⁻⁸ cm.

 How would you account the following :

 Transition metals and their compounds show catalytic properties.

Account for the following :

Reducing character decreases from SO2 to TeO₂.

Outline the principles behind the refining of metals by the following methods:

Zone refining method

Outline the principles behind the refining of metals by the following methods:

Chromatographic method

Write the principle behind the following methods of refining:

Vapour-phase refining

Write the product formed on reaction of D-glucose with Br₂ water.

Write the principles of the following methods :

Froth floatation method

Write down the reaction taking place in blast furnace related to the metallurgy of iron in the temperature rnge 500 K – 800 K. What is the role of limestone in the metallurgy of iron? 

What happens when Copper matte is charged into silica lined converter and hot air blast is blown? 

Write chemical equation in support of your answer. 
 Out of   Cl and  CH₂- Cl,  which one is more reactive towards nucleophilic substitution reaction and why? 

Name the method of refining which is Used to obtain semiconductor of high purity. 

Name the method of refining which is Used to obtain low boiling metal.

Write chemical reactions taking place in the extraction of copper from Cu₂ S. 

Why dextro and laevorotatory isomers of Butan-2-ol are difficult to separate by fractional distillation?