1. Ammoniacal nitrogen can be determined by treatment of the sample with chloroplatinic acid; the product is slightly soluble ammonium chloride palatinate
H2PtCl6 + 2NH4 + → (NH4)2PtCl6 + 2H+
The precipitate decomposes on ignition, yielding metallic platinum and gaseous products:
(NH4)2PtCl6 → Pt(s) + 2Cl2 (g) + 2NH3 (g) + 2HCl
Calculate the percentage ammonia in a sample if 0.2115 gram gave rise to 0.4693 gram of platinum.

2. A series of sulphate samples is to be analysed by precipitation as BaSO4. If it is known that the sulphate content in these samples ranges between 20% and 55%, what minimum sample mass should be taken to ensure that a precipitate mass no smaller than 0.200 gram is produced? What is the maximum precipitate weight to be expected if this quantity of sample is taken.