20 g of a mixture of red and white phosphorus was treated with a solvent – carbon disulfide.

20 g of a mixture of red and white phosphorus was treated with a solvent – carbon disulfide. The remaining insoluble precipitate was isolated and weighed. Its weight was 12.6 g. Calculate the mass and mass fraction of white phosphorus in the initial mixture.

Red phosphorus can be obtained by heating white phosphorus. After a series of procedures (we will not go into details), white phosphorus does not completely turn into red. Therefore, a CS2 solution is poured into the container with the contents, in which red phosphorus remains at the bottom, and white phosphorus floats to the surface.

Accordingly, we have red phosphorus as a sediment, the mass of which is 12.6 g.

m (Pbel) = 20 – 12.6 = 7.4 g.

w = 7.4 / 20 = 37% of the total mass of the mixture.