Common sense tells us that 1 atom of lead and 25 atoms of mercury can’t be the answer because the amounts are much smaller than the other options.
To compare the remaining options, we first find their masses individually. No need to worry about significant figures because this is a comparison of the two.
[tex](0.3 \text{ mol Au})(\frac{196.97 \text{ g}}{1 \text{ mol}} )=59.091 \text{ g Au}\\(0.5 \text{ mol Ag})(\frac{107.87 \text{ g}}{1 \text{ mol}} )=53.935 \text{ g Ag}[/tex]
Because 59.091 g is greater than 53.935 g, the 0.3 mol of gold atoms has the greatest mass.
