# Chemistry Help!

1. Mar 8, 2006

### Nimmy

My sister tried many ways to get this solution but it didnt work so she needs your help on how to do this problem. Plz Plz Plz do it before 10:00 PM. :surprised

2C2H4 (g) + Br2 (g) + Cl2 (g) -----) 2C2H4ClBr(g)

A Skyline student reacts 15 L of C2H4, 20 L of Br2 (g) and 10 L of Cl2 to form C2H4ClBr(g). Assume the gasses begin the reaction at STP.

Which reactant is the limiting reagent?

2. Mar 9, 2006

### mrjeffy321

From the balanced chemical reaction , you know the mole ratios of all the products to each other (2 moles C2H4 : 1 mole Br2 : 1 mole Cl2).

Since you know the volumes of each gas used in the reaction and their temperature and pressure (STP), you can find the mole ratios present at the start of the reaction. At STP, an ideal gas has a volume of 22.4 Liters, so from this, we can calculate the number of moles of each gas. After knowing the number of moles actually present, compare it to how many moles should be there of the other gasses, minimum, assuming that the gas in question is not the limiting reactant.

For example,
20 Liters of Br2 is about .892 moles of Br2, so in theory, there should be at least .892 moles of Cl2 and 1.784 moles of C2H4. Are there? If there is too much of the other reactants, it is possible that the gas in question is the limiting reactant.

Last edited: Mar 9, 2006