Question

1)A system at equilibrium contains I2(g) at a pressure of 0.10 atm and I(g) at a pressure of 0.16 atm . The system is then compressed to half its volume. A)Find the pressure of I2 when the system returns to equilibrium. Express your answer to two significant figures and include the appropriate units.

i got 0.27 and was wrong

2)Solid carbon can react with gaseous water to form carbon monoxide gas and hydrogen gas. The equilibrium constant for the reaction at 700.0 K is Kp=1.60×10−3.

If a 1.55-L reaction vessel initially contains 153 torr of water at 700.0 K in contact with excess solid carbon, find the percent by mass of hydrogen gas of the gaseous reaction mixture at equilibrium. mH2/ mH2+mCO+mH2O =    %

Answer 1

1)

I2 (g) <-----> 2 I (g)
Kp = (pI)^2 / p(I2)
=0.16^2 / 0.10
=0.256

when volume become half, pressure will double
I2 (g) <-----> 2 I (g)
0.20 0.32 (initial)
0.20+x 0.32-2x (at equilibrium)
Kp = (pI)^2 / p(I2)
= (0.32-2x)^2 / (0.20+x)
0.256 (0.20+x) = 4x^2 + 0.1024 -1.28 x
0.0512 + 0.256*x = 4x^2 + 0.1024 -1.28 x
4x^2 - 1.536*x + 0.0512 = 0
solving above quadratic equation we get,
x = 0.347 and x=0.0368

x can't be 0.347 as in this case pressure of I will become negative
so,
x = 0.0368
pI2 = 0.20+x = 0.20 + 0.0368 = 0.24 atm
Answer: 0.24 atm

I am allowed to answer only 1 question at a time