Final answer:
To produce 0.05 mol of Au2S, a total of 19.7 grams of Au was produced. Thus, the mass of Au produced is 0.1 mol * 197.0 g/mol = 19.7 g.
Step-by-step explanation:
To calculate the mass of gold produced when 0.05 mol of Au2S is reduced completely with excess H2, we need to use the molar ratio between Au2S and Au.
The balanced equation for the reaction is: Au2S + 2H2 -> 2Au + H2S.
From the equation, we can see that for every 1 mol of Au2S, 2 mol of Au is produced.
Therefore, 0.05 mol of Au2S will produce 0.1 mol of Au.
To find the mass of Au, we can use the molar mass of Au which is 197.0 g/mol.
Thus, the mass of Au produced is 0.1 mol * 197.0 g/mol = 19.7 g.