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 NH3 and PH3. Phosphine is a flammable gas and is prepared from white phosphorous. 1. 64. Among the following, the correct statement is   Phosphates have no biological significance in humans   Between nitrates and phosphates, phosphates are less abundant in earth's crust   Between nitrates and phosphates, nitrates are less abundant in earth's crust   Oxidation of nitrates is possible in soil   Hint Half-n-half Clue   2. 65. Among the following, the correct statement is   Between NH3 and PH3, NH3 is a better electron donor because the lone pair of electrons occupies spherical 's' orbital and is less directional   Between NH3 and PH3, PH3 is a better electron donor because the lone pair of electrons occupies sp3 orbital and is more directional   Between NH3 and PH3, NH3 is a better electron donor because the lone pair of electrons occupies sp3 orbital and is more directional   Between NH3 and PH3, PH3 is a better electron donor because the lone pair of electrons occupies spherical 's' orbital and is less directional   Half-n-half Clue   3. 66. White phosphorus on reaction with NaOH gives PH3 as one of the products. This is a   dimerization reaction   disproportionation reaction   condensation reaction   precipitation reaction   Half-n-half Clue