Final answer:
To determine the moles of Ag₂S formed if 85.0 g Na₂S is used, we need to convert the mass of Na₂S to moles.
Step-by-step explanation:
In the reaction 2AgI + Na₂S → Ag₂S +2NaI, the stoichiometric ratio tells us that for every 2 moles of AgI reacted, 1 mole of Ag₂S is formed. To determine the moles of Ag₂S formed if 85.0 g Na₂S is used, we need to convert the mass of Na₂S to moles:
Moles Na₂S = mass Na₂S / molar mass Na₂S
Calculate the molar mass of Na₂S: 22.99 g/mol (atomic mass of Na) * 2 + 32.07 g/mol (atomic mass of S)
Molar mass = 46.00 g/mol
Now, calculate the moles of Na₂S: 85.0 g / 46.00 g/mol