68. Solving a chemistry problem

2. A. Precipitated and weight forms of sediment. What requirements must they meet?
B. Describe the sequence of gravimetric determination of iron in vitriol (FeSO4*7H2O). Under what conditions and why should precipitation be carried out? Calculate the optimal weight of iron sulfate sample and the volume of 10.4% ammonia solution, the density of which is 0.956 g/cm3, necessary for the complete precipitation of iron (III) hydroxide.