Science (English Medium) Class 12 - CBSE Question Bank Solutions for Chemistry

Explain why does conductivity of germanium crystals increase on doping with galium.

How does the doping increase the conductivity of semiconductors?

Match the types of colloidal systems given in Column I with the name given in Column II.

What is the role of adsorption in froth floatation process used especially for concentration of sulphide ores?

Which of the following statements are correct?

(i) S – S bond is present in \[\ce{H2S2O6}\].

(ii) In peroxosulphuric acid \[\ce{(H2SO5)}\] sulphur is in +6 oxidation state.

(iii) Iron powder along with \[\ce{Al2O3}\] and \[\ce{K2O}\] is used as a catalyst in the preparation of \[\ce{NH3}\] by Haber’s process.

(iv) Change in enthalpy is positive for the preparation of \[\ce{SO3}\] by catalytic oxidation of \[\ce{SO2}\].

Write the main product in the following reaction:

What is ferromagnetism?

Iron (z=26) is highly ferromagnetic. Explain.

What type of magnetism is shown in the following alignment of magnetic moments?

Account for the following: Fluorine does not exhibit positive oxidation state.

Fluorine is a stronger oxidising agent than chlorine. Why?

What type of magnetism is shown by a substance if magnetic moments of domains are arranged in same direction?

What is the difference between a nucleoside and nucleotide?

Compare the oxidizing action of F₂ and Cl₂ by considering parameters such as bond dissociation enthalpy, electron gain enthalpy and hydration enthalpy.

Account for the following :

Acidic character increases from HF to HI.

F₂ has lower bond dissociation enthalpy than Cl₂. Why?

Define the following term:

Ferromagnetism

Which halogen compound in the following pair will react faster in S_N2 reaction CH₃Br or CH₃I.

Which halogen compound in each of the following pairs will react faster in S_N2 reaction

(CH₃)₃ C – Cl or CH₃ – Cl

Write the type of magnetism observed when the magnetic moments are oppositely aligned and cancel out each other.