When 2.47 g of chromium is reacted with an excess of sulphur, the compound Cr2S3 results. Treating the Cr2S3 so formed with strontium metal converts all of the sulphur to SrS. Reacting the SrS with sodium metal then converts all the SrS to Na2S. What mass in grams of Na2S is produced?

Answer 1

1. First you must write the equations and balance them.
2. Convert 2.47 g Cr to mols remembering that mols = grams/atomic mass.
3. Convert mols Cr to mols Na2S using the coefficients in the balanced equations.
4. Convert mols Na2S to grams using grams = mols x molar mass.

Note: You CAN simply do this as three or four problem and determine the mols Cr2S3 formed, then mols SrS formed, then mols Na2S formed but that is the long way of doing it. Post your work if you get stuck.