Tricky Gas Stoichiometry Problem?

Question

What volume of bromine gas is produced if 75.2 g of Cl2 react wwith excess HBR? The bromine is at 25 degrees C and 105.8 kPa?

Cl2 + 2 HBR --> Br2 + 2HCl

How do you do this? It's kind of confusing...Thanks for the help!

Answer 1

75.2 g Cl2 * (1 mol Cl2/70.906 g)*(1 mol Br2/1 mol Cl2) = 1.06 mol Br2

PV = nRT

V = nRT/P

V = (1.06)(8.31)(298)/(105.8)

V = 24.8 L

*Sorry. I had it wrong at first, but now the answer is perfect!

Answer 2

First, you separate the gas volume problem from the stoichiometry problem.

The reaction for the stoich. problem is there. You create one mole of bromine for each mole of chlorine that goes in. You have slightly more than 1 mole of Cl2 (the dimer) and should wind up with the same moles of Br2(the dimer).

HOWEVER, at STP, which is pretty close to what your final conditions are, bromine is a liquid, so the volume of bromine (as gas) should be virtually zero.