Question

12. How many molecules of hydrogen gas are needed to react with CS, to produce 2.50 L of CH, at STP?4H2(3)+CS (1) CH (8) + 2H2S(3)

Answer 1

In this question, we have the following reaction:

4 H2 + CS2 -> CH4 + 2 H2S

We have:

2.50 L of CH4

Something important in this question is that STP means Standard Temperature and Pressure, and at these conditions, 1 mol of gas will be equal to 22.4 Liters of volume, so if we have 2.50 Liters of CH4, this means:

22.4 = 1 mol

2.50 = x moles

x = 0.112 moles of CH4

Now we know the number of moles of CH4, to find out the number of moles of H2, we need to use the concept of molar ratio, in which the number in front of the compound (called stoichiometric coefficients), represents how many moles we need of each one, we have:

4 H2 = 1 CH4

x H2 = 0.112 CH4

x = 0.448 moles of H2 are needed to produce 0.112 moles of CH4