1. The problem statement, all variables and given/known data The following reaction has Kp = 55.5 at 700 K: H2(g) + I2(g) <-> 2HI(g) You introguce 2.00 moles of H2(g) and 1.00 mole of I2(g) into a previously evacuated 5.00 L flash, and then heat the flask to 700 K. What mass of HI(g) will be present at eqilibrium? 2. Relevant equations PV=nRT Kp 3. The attempt at a solution The pressure of 3 moles in 5L at 700K is 34.4652atm. So for every atm the reactant pressure decreases the product pressure increases the same. I get x^2 / (34.4652-x) = 55.6 => x=24.0466atm. I covert that to mol using pv=nrt and then multiply by the molecular wight of HI and get around 250 or 260 g *i forgot to wrrite it down). The answer however is 240g and every method I try I always get over by around 20 which doesn't seem right. Can you tell what I'm doing wrong? Thanks for any help.