Chemistry 12 Chapter 8 Exemplar Solutions the P and F Block Elements Part 2

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Question 9:

When solution is added to oxalic acid solution, the decolourisation is slow in the beginning but becomes instantaneous after some time because

(i) is formed as the product.

(ii) Reaction is exothermic.

(iii) catalyses the reaction.

(iv) acts as autocatalyst.

Answer: (iv)

Question 10:

There are 14 elements in actinoid series. Which of the following elements does not belong to this series?

(i)

(ii)

(iii)

(iv)

Answer: (iii)

Question 11:

KMnO4 acts as an oxidising agent in acidic medium. The number of moles of KMnO4 that will be needed to react with one mole of sulphide ions in acidic solution is

(i)

(ii)

(iii)

(iv)

Answer: (i)

Question 12:

Which of the following is amphoteric oxide?

(i)

(ii)

(iii)

(iv)

Answer: (i)

Question 13:

Gadolinium belongs to series. It’s atomic number is . Which of the following is the correct electronic configuration of gadolinium?

(i)

(ii)

(iii)

(iv)

Answer: (i)

Question 14:

Interstitial compounds are formed when small atoms are trapped inside the crystal lattice of metals. Which of the following is not the characteristic property of interstitial compounds?

(i) They have high melting points in comparison to pure metals.

(ii) They are very hard.

(iii) They retain metallic conductivity.

(iv) They are chemically very reactive.

Answer: (i)

Question 15:

The magnetic moment is associated with its spin angular momentum and orbital angular momentum. Spin only magnetic moment value of ion is ___________.

(i)

(ii)

(iii)

(iv)

Answer: (ii)

Question 16:

acts as an oxidising agent in alkaline medium. When alkaline is treated with , iodide ion is oxidised to ____________.

(i)

(ii)

(iii)

(iv)

Answer: (iii)

Question 17:

Which of the following statements is not correct?

(i) Copper liberates hydrogen from acids.

(ii) In its higher oxidation states, manganese forms stable compounds with oxygen and fluorine.

(iii) and are oxidising agents in aqueous solution.

(iv) and are reducing agents in aqueous solution.

Answer: (i)

Question 18:

When acidified solution is added to salts then changes to

(i)

(ii)

(iii)

(iv)

Answer: (iii)

Question 19:

Highest oxidation state of manganese in fluoride is but highest oxidation state in oxides is because ____________.

(i) Fluorine is more electronegative than oxygen.

(ii) Fluorine does not possess d-orbitals.

(iii) Fluorine stabilises lower oxidation state.

(iv) In covalent compounds fluorine can form single bond only while oxygen forms double bond.

Answer: (iv)

Question 20:

Although Zirconium belongs to transition series and Hafnium to transition series even then they show similar physical and chemical properties because___________.

(i) Both belong to d-block.

(ii) Both have same number of electrons.

(iii) Both have similar atomic radius.

(iv) Both belong to the same group of the periodic table.

Answer: (iii)

Question 21:

Why is not used to make the medium acidic in oxidation reactions of in acidic medium?

(i) Both and act as oxidising agents.

(ii) oxidises into which is also an oxidising agent.

(iii) is a weaker oxidising agent than .

(iv) acts as a reducing agent in the presence of HCl.

Answer: (ii)

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