## Chemistry and Chemical Reactivity (9th Edition)

a) Number of moles of $SO_2$: $500.\ g\div 64.06\ g/mol= 7.805\ mol$ Number of moles of Zn: $125\ kg\div 65.38\ kg/kmol=1.91\ kmol$ $SO_2$ is the limiting reactant. From stoichiometry: $7.805\ mol\times 1\ mol\ ZnS_2O_4/2\ mol\ SO_2\times 1\ mol\ Na_2S_2O_4/1\ mol\ ZnS_2O_4\times 174.10\ g/mol=679.4\ g\ Na_2S_2O_4$ b) Mass percentage definition: $90.1/100*679.41=612\ g$