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

How are metals used as semiconductors refined? What is the principle of the method used?

Give two requirements for vapour phase refining.

Match the items of Column I with the items of Column II and assign the correct code:

Assertion: Nickel can be purified by Mond process.

Reason: \[\ce{Ni(CO)4}\] is a volatile compound which decomposes at 460 K to give pure Ni.

Assertion: Zirconium can be purificed by Van Arkel method.

Reason: ZrI₄ is volatile and decomposes at 1800 K.

Assertion: Zone refining method is very useful for producing semiconductors.

Reason: Semiconductors are of high purity.

Assertion: Hydrometallurgy involves dissolving the ore in a suitable reagent followed by precipitation by a more electropositive metal.

Reason: Copper is extracted by hydrometallurgy.

Explain the following:

Vapour phase refining method is used for the purification of Ti.

Which of the following is not tetrahedral in shape?

On addition of small amount of \[\ce{KMnO4}\] to concentrated \[\ce{H2SO4}\], a green oily compound is obtained which is highly explosive in nature. Identify the compound from the following.

Which of the following reactions are disproportionation reactions?

(a) \[\ce{Cu^{+} -> Cu^{2+} + Cu}\]

(b) \[\ce{3MnO^{-}4 + 4H^{+} -> 2MnO^{-}4 + MnO2 + 2H2O}\]

(c) \[\ce{2KMnO4 -> K2MnO4 + MnO2 + O2}\]

(d) \[\ce{2MnO^{-}4 + 3Mn^{2+} + 2H2O -> 5MnO2 + 4H^{+}}\]

Which of the following is amphoteric oxide?

\[\ce{Mn2O7, CrO3, Cr2O3, CrO, V2O5, V2O4}\]

\[\ce{KMnO4}\] acts as an oxidising agent in alkaline medium. When alkaline \[\ce{KMnO4}\]  is treated with \[\ce{KI}\], iodide ion is oxidised to ______.

Generally transition elements and their salts are coloured due to the presence of unpaired electrons in metal ions. Which of the following compounds are coloured?

(i) \[\ce{KMnO4}\]

(ii) \[\ce{Ce(SO4)2}\]

(iii) \[\ce{TiCl}\]

(iv) \[\ce{Cu2 Cl2}\]

In the form of dichromate, \[\ce{Cr (VI)}\] is a strong oxidising agent in acidic medium but \[\ce{Mo (VI)}\] in \[\ce{MoO3}\] \[\ce{and W (VI)}\] in \[\ce{WO3}\] are not because:

(i) \[\ce{Cr(VI)}\] is more stable than \[\ce{Mo(VI)}\] and  \[\ce{and W(VI)}\].

(ii) \[\ce{Mo(VI)}\] and \[\ce{and W(VI)}\] are more stable than  \[\ce{Cr(VI)}\].

(iii) Higher oxidation states of heavier members of group-6 of transition series are more stable.

(iv) Lower oxidation states of heavier members of group-6 of transition series are more stable.

When \[\ce{Cu^2+}\] ion is treated with \[\ce{KI}\], a white precipitate is formed. Explain the reaction with the help of chemical equation.

When orange solution containing \[\ce{Cr2O^{2-}7}\] ion is treated with an alkali, a yellow solution is formed and when \[\ce{H^+}\] ions are added to yellow solution, an orange solution is obtained. Explain why does this happen?

The colour of the coordination compounds depends on the crystal field splitting. What will be the correct order of absorption of wavelength of light in the visible region, for the complexes, \[\ce{[Co(NH3)6]^{3+}}\], \[\ce{[Co(CN)6]^{3-}}\], \[\ce{[Co(H2O)6]^{3+}}\]

The CFSE for octahedral \[\ce{[CoCl6]^{4-}}\] is 18,000 cm^–1. The CFSE for tetrahedral \[\ce{[CoCl4]^{2-}}\] will be ______.

Atomic number of \[\ce{Mn}\], \[\ce{Fe}\] and \[\ce{Co}\] are 25, 26 and 27 respectively. Which of the following inner orbital octahedral complex ions are diamagnetic?

(i) \[\ce{[Co(NH3)6]^{3+}}\]

(ii) \[\ce{[Mn(CN)6]^{3-}}\] 

(iii) \[\ce{[Fe(CN)6]^{4-}}\]

(iv) \[\ce{[Fe(CN)6]^{3-}}\]