Question

Photographic film contains silver bromide in gelatin. Once exposed, some of the silver bromide decomposes, producing fine grains of silver. The unexposed silver bromide is removed by treating the film with sodium thiosulfate. Soluble sodium silver thiosulfate (Na3Ag(S2O3)2) is produced.
AgBr(s) + 2 Na2S2O3(aq) Na3Ag(S2O3)2(aq) + NaBr(aq)

Determine the mass of Na3Ag(S2O3)2 produced if 0.430 g AgBr is removed.

Answer 1

Here is a solved example of a stoichiometry problem such as this one. Just follow the steps.
http://www.jiskha.com/science/chemistry/stoichiometry.html

Answer 2

Chloroform (CHCl3), an important solvent, is produced by a reaction between methane and chlorine.
CH4(g) + 3 Cl2(g) CHCl3(g) + 3 HCl(g)
How many grams of CH4 is needed to produce 39.0 g CHCl3?