Mercury can be obtained by reacting mercury (II) sulfide with

calcium oxide. How many grams of mercury (II) sulfide are

needed to produce 26.0 g of Cas?

4HgS (s) + 4CaO (s) - 411g () + 3CaS (s) + Caso.

111.68 g

Explanation:

Given dа ta:

Mass of HgS needed = ?

Mass of CaS produced = 26.0 g

Solution:

Chemical equation;

4HgS + 4CaO → 4Hg + 3CaS + CaSO₄

Number of moles of CaS:

Number of moles = mass/molar mass

Number of moles = 26 g / 72.143 g/mol

Number of moles = 0.36 mol

Now we will compare the moles of HgS with CaS.

CaS : HgS

3 : 4

0.36 : 4/3*0.36 = 0.48 mol

Mass of HgS:

Mass = number of moles * molar mass

Mass = 0.48 mol * 232.66 g/mol

Mass = 111.68 g