How many grams of mercury are needed to react completely with 157g of sulfur to form hgs?

To solve this we need to balance the equations first.

So Hg + S - - > HgS is balanced

One mole of Hg requires one mole of S to form one mole of HgS.

Number of moles of Sulphur = mass / molar mass = 157/32 = 4.906

So 4.90 moles of S reacts with 4.90 moles of Hg.

Hence there are 4.90 moles of 4.90 of Hg.

Mass = number of moles * molar mass of Hg

Mass = 4.906 * 200.59 = 982.891g