The reaction
H2(g) + I2(g) <===> 2HI(g)
has Kp = 45.9 at 763 K. A particular equilibrium mixture at that temperature contains gaseous HI at a partial pressure of 4.00 atm and hydrogen gas at a partial pressure of 0.273 atm. What is the partial pressure of I2?
A) 10.7 atm
B) 0.273 atm
C) 1.28 atm
D) 58.6 atm
E) 0.319 atm