Science (English Medium) इयत्ता १२ - CBSE Question Bank Solutions for Chemistry

When concentrated sulphuric acid was added to an unknown salt present in a test tube a brown gas (A) was evolved. This gas intensified when copper turnings were added to this test tube. On cooling, the gas (A) changed into a colourless solid (B).

1) Identify (A) and (B).

2) Write the structures of (A) and (B).

3) Why does gas (A) change to solid on cooling?

Give one example each of 'oil in water' and 'water in oil' emulsion.

What type of linkage is responsible for the formation of proteins?

Write the product formed when glucose is treated with HI ?

 Complete and balance the following equations: 
S+H₂SO₄(conc.)  → 

Answer the following question.
What is the difference between an emulsion and a gel?

A group of 14 elements is converted into n-type semiconductor by doping it with:

Group 14 element is converted to p-type semiconductor by doping it with:

In n-type semiconductor, current is carried by ____________.

Which transition metal oxide has appearance and conductivity like that of copper?

In the manufacture of sulphuric acid by contact process Tyndall box is used to ____________.

The cell membranes are mainly composed of:

To get n-type of semiconductor, germanium should be doped with ____________.

p-type semiconductors are formed when Si or Ge are doped with ____________.

Hot conc. \[\ce{H2SO4}\] acts as the moderately strong oxidising agent. It oxidises both metals and non-metals. Which of the following element is oxidised by conc. \[\ce{H2SO4}\] into two gaseous products?

Which of the following oxides behaves as conductor or insulator depending upon temperature?

Which of the following is true about the charge acquired by p-type semiconductors?

To get a n-type semiconductor from silicon, it should be doped with a substance with valence ______.

Under the influence of electric field, which of the following statements is true about the movement of electrons and holes in a p-type semiconductor?

(i) Electron will move towards the positvely charged plate through electron holes.

(ii) Holes will appear to be moving towards the negatively charged plate.

(iii) Both electrons and holes appear to move towards the positively charged plate.

(iv) Movement of electrons is not related to the movement of holes.

A perfect crystal of silicon (Figure) is doped with some elements as given in the options. Which of these options show n-type semiconductors?