Science (English Medium) कक्षा १२ - CBSE Question Bank Solutions

Which of the following represents correct order of conductivity in solids?

Which of the following statements are true about metals?

(i) Valence band overlaps with conduction band.

(ii) The gap between valence band and conduction band is negligible.

(iii) The gap between valence band and conduction band cannot be determined.

(iv) Valence band may remain partially filled.

Assertion: Graphite is a good conductor of electricity however diamond belongs to the category of insulators.
Reason: Graphite is soft in nature on the other hand diamond is very hard and brittle.

Which of the following statements are correct?

(i) Among halogens, radius ratio between iodine and fluorine is maximum.

(ii) Leaving F – F bond, all halogens have weaker X – X bond than X – X' bond in interhalogens.

(iii) Among interhalogen compounds maximum number of atoms are present in iodine fluoride.

(iv) Interhalogen compounds are more reactive than halogen compounds.

Silver crystallises in F.C.C. (face-centred cubic crystal) structure. The edge length of the unit cell is found to be 408.7 pm. Calculate density of the unit cell.

[Given: Molar mass of silver is 108 g mol^-1 ]

What happens when 

(i) PCl₅ is heated ? Write the reactions involved.

Give the reason for bleaching action of Cl₂.

Name two poisonous gases which can be prepared from chlorine gas.

How can you prepare Cl₂ from HCl ? Write reaction only.

Write balanced equations for chlorine gas is passed into a solution of NaI in water.

Determine the density of Cesium chloride which crys tallizes in BCC type structure with the edge length 412.1 pm. The atomic masses of Cs and Cl are 133 and 35.5 respectively.

Which type of solid conduct electricity in molten state but not in solid state?

In which the NH₃ is not used?

H₂S does not produce metallic sulphide with:

Chlorine acts as a bleaching agent only in presence of ____________.

When chlorine reacts with a cold and dilute solution of sodium hydroxide, it forms:

The correct order of bond angles in the following species is:

When Cl₂ reacts with hot and conc. NaOH, the oxidation number of chlorine changes from ____________.

Chlorine reacts with excess of NH₃ to form:

Assertion: \[\ce{NaCl}\] reacts with concentrated \[\ce{H2SO4}\] to give colourless fumes with pungent smell. But on adding \[\ce{MnO2}\] the fumes become greenish yellow.

Reason: \[\ce{MnO2}\] oxidises \[\ce{HCl}\] to chlorine gas which is greenish yellow.