IIT-JEE 2008 · Paper 1 · Chemistry Q66

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ChemistrySingle correct+4 / -1Question 66 of 69

Passage

Paragraph for Question Nos. 64 to 66

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. Hybridization easily explains the ease of sigma donation capability of $\ce{NH3}$ and $\ce{PH3}$ . Phosphine is a flammable gas and is prepared from white phosphorous.

White phosphorus on reaction with NaOH gives $\ce{PH3}$ as one of the products. This is a

dimerization reaction

disproportionation reaction

condensation reaction

precipitation reaction

Answer and worked solution

Official answer: B

$\ce{P4 + 3NaOH + 3H2O -> PH3 + 3NaH2PO2}.$
Phosphorus (0) is both reduced to −3 (phosphine) and oxidised to +1 (hypophosphite): a disproportionation.

(B)

Topics:Group 15 Oxidation number

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IIT-JEE 2008 · Paper 1, Chemistry question 66