pBlock ElementsII 1 Question 64
Passage
There are some deposits of nitrates and phosphates in earth’s crust. Nitrates are more soluble in water. Nitrates are difficult to reduce under the laboratory conditions but microbes do it easily. Ammonia forms large number of complexes with transition metal ions. Hybridisation easily explains the ease of sigma donation capability of $\mathrm{NH}_3$ and $\mathrm{PH}_3$. Phosphine is a flammable gas and is prepared from white phosphorus.
$(2008,3 \times 4 M=12 M)$
59. Among the following, the correct statement is
(a) Between $\mathrm{NH} _{3}$ and $\mathrm{PH} _{3}, \mathrm{NH} _{3}$ is a better electron donor because the lone pair of electrons occupies spherical ’ $s$ ’ orbital and is less directional
(b) Between $\mathrm{NH} _{3}$ and $\mathrm{PH} _{3}, \mathrm{PH} _{3}$ is a better electron donor because the lone pair of electrons occupies $s p^{3}$-orbital and is more directional
(c) Between $\mathrm{NH} _{3}$ and $\mathrm{PH} _{3}, \mathrm{NH} _{3}$ is a better electron donor because the lone pair of electrons occupies $s p^{3}$-orbital and is more directional
(d) Between $\mathrm{NH} _{3}$ and $\mathrm{PH} _{3}, \mathrm{PH} _{3}$ is a better electron donor because the lone pair of electrons occupies spherical ’ $s$ ’ orbital and is less directional
Show Answer
Answer:
Correct Answer: 59. (c)
Solution:
$\mathrm{NH} _{3}$ is stronger Lewis base than $\mathrm{PH} _{3}$. In a group of hydrides, basic strength decreases down the group.
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