Chemistry Labs

International Chemistry Olympiad · 1976

Problems

  1. Problem 2A sample of 2.3793 g of a crystallohydrate of the type MXxAXy ⋅ z HX2O\ce{M_xA_y . z H2O} (where M is a metal) reacted with an excess of SOClX2\ce{SOCl2}. The gaseous products were absorbed in an aqueous solution containing barium chloride, hydrochloric acid and hydrogen peroxide. Small carried-over amounts of SOClX2\ce{SOCl2} had been frozen out. The mass of the deposited precipitate was 14.004 g and contained 13.74 mass % of sulphur. In another experiment, 1.1896 g of the initial hydrate was dissolved in water and made up to 100 cm3^3. One fifth of this solution required 10 cm3^3 of 0.2 M AgNOX3\ce{AgNO3} solution for complete precipitation (yielding 0.28664 g of precipitate). (a) Calculate the formula of the crystallohydrate. (b) Given that the hydrate can contain at most 7 moles of water per mole of hydrate, name another hypothetical hydrate that is ruled out by this limit.Solutions: 1