chemical equations

Question

Chloroform (CHCl₃), an important solvent, is produced by a reaction between methane and chlorine.

CH₄(g) + 3 Cl₂(g)  CHCl₃(g) + 3 HCl(g)

How many grams of CH₄ is needed to produce 52.0 g CHCl₃?

Answer 1

First thing is to note what you are given. We are given 52.0g CHCl3. Always start with the givens in a problem.

1. We want to find the number of moles of CHCl3 that were produced in order to know how much CH4 was used to make it. So we have a given that is in grams. In order to determine the number of moles we are going to divide the amount given by the molar mass of CHCl3.
2. The next step is to determine how many moles of CH4 were used to make CHCl3. If we look at the balanced equation we see that there is only 1 mole of CH4 (there are no coefficients in front of CH4). we now multiply the number of moles.
3. Once we determine the number of moles of CH4, we can use its molar mass to determine how many grams were needed.
4. Make sure we use Significant figures

52.0g CHCl3 x 1mol CHCl3/119.3776 g/mole CHCl3 = .436 moles CHCl3

.436 moles CHCl3 x 1mol CH4(what we are looking for)/1 mol CHCl3 = .436 mol CH4

.436 mol CH4 x 16.0425 g/mol CH4 = 6.99 g of CH4 are needed.