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37
MCQ (Multiple Correct Answer)

Which of the following statements are true?

A
Only type of interactions between particles of noble gases are due to weak dispersion forces.
B
  Ionisation enthalpy of molecular oxygen is very close to that of xenon.
C
Hydrolysis of $\mathrm{XeF}_6$ is a redox reaction.
D
Xenon fluorides are not reactive.
38
Subjective

In the preparation of $\mathrm{H}_2 \mathrm{SO}_4$ by Contact process, why is $\mathrm{SO}_3$ not absorbed directly in water to form $\mathrm{H}_2 \mathrm{SO}_4$ ?

Explanation

In Contact process $\mathrm{SO}_3$ is not absorbed directly in water to from $\mathrm{H}_2 \mathrm{SO}_4$ because the reaction is highly exothermic, acid mist is formed. Hence, the reaction becomes difficult to handle.

Note

39
Subjective

Write a balanced chemical equation for the reaction showing catalytic oxidation of $\mathrm{NH}_3$ by atmospheric oxygen.

Explanation

Ammonia $\left(\mathrm{NH}_3\right)$ on catalytic oxidation by atmospheric oxygen in presence of $\mathrm{Rh} / \mathrm{Pt}$ gauge at 500 K under pressure of 9 bar produces nitrous oxide.

Balanced chemical reaction can be written as

$4 \mathrm{NH}_3+\underset{\text { From air }}{5 \mathrm{O}_2}\xrightarrow[500 \mathrm{~K} ; 9 \mathrm{bar}]{\mathrm{Pt} / \text { Rh gauge catalyst }}4 \mathrm{NO}+6 \mathrm{H}_2 \mathrm{O}$

40
Subjective

Write the structure of pyrophosphoric acid.

Explanation

Molecular formula of pyrophosphoric acid is $\mathrm{H}_4 \mathrm{P}_2 \mathrm{O}_7$ and its structure is as follows

41
Subjective

$\mathrm{PH}_3$ forms bubbles when passed slowly in water but $\mathrm{NH}_3$ dissolves. Explain why?

Explanation

Dissolution of $\mathrm{NH}_3$ and $\mathrm{PH}_3$ in water can be explained on the basis of H -bonding. $\mathrm{NH}_3$ forms H -bond with water so it is soluble but $\mathrm{PH}_3$ does not form H -bond with water so it remains as gas and forms bubble in water.