Chapter 21, Problem 21.139MP

Chromium forms three isomeric compounds A, B, and C with percent composition 19.52% Cr, 39.91% Cl, and40.57% ${\text{H}}_{\text{2}}\text{O}$ . When a sample of each compound was dissolved in water and aqueous ${\text{AgNO}}_{\text{3}}$ was added, a precipitate of AgCl formed immediately. A 0.225-g sample of compound A gave 0.363 g of AgCl, 0.263 g of B gave0.283 g of AgCl, and 0.358 g of C gave 0.193 g of AgCl.One of the three compounds is violet, while the other two are green. In all three, chromium has cocrdination number 6.
(a) What are the empirical formulas of A, B, and C?
(b) What are the probable structural formulas of A, B, andC? Draw the structure of the cation in each compound.Which cation can exist as diastereo isomers?
(c) Which of the three compounds ¡s likely to be the violetone? Explain.
(d) What are the approximate freezing points of 0.25 m solutions of A, B, and C, assuming complete dissociation?