Answer:
C. 2.
Explanation:
The total reaction order of this reaction is second order (2). For a second order reaction ,the rate depends on two variable concentration terms which may or may not be same.
Given that:
Two reactants combine to form a product in the reaction A + B → C
The above reaction is bimolecular as two molecules are involved in the reaction.
If
and
are the concentrations of A and B respectively at any time t, then assuming that the reaction is of first order with respect to both A and B , the overall order is second and the reaction rate is given by:

where;
= specific rate constant for a second order reaction and becomes the rate of the reaction when both
and
are unity.
Based on experiment 1:
Mass of Hg = 1.00 g
Mass of sulfide = 1.16 g
Mass of sulfur = 1.16 - 1.00 = 0.16 g
# moles of Hg = 1 g/200 gmol-1 = 0.005 moles
# moles of S = 0.16/32 gmol-1 = 0.005 moles
The Hg:S ratio is 1:1, hence the sulfide is HgS
Based on experiment 2:
Mass of Hg taken = 1.56 g
# moles of Hg = 1.56/200 = 0.0078
Mass of S taken = 1.02 g
# moles of S = 1.02/32 = 0.0319
Hence the limiting reagent is Hg
# moles of Hg reacted = # moles of HgS formed = 0.0078 moles
Molar mass of HgS = 232 g/mol
Therefore, mass of HgS formed = 0.0078 * 232 = 1.809 g = 1.81 g
The answer to this question is 10.038
A and 3
B and 6
C and 5
D and 1
E and 2
F and 4