Textbook 5I.3

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Megan Singer 3D
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Textbook 5I.3

Postby Megan Singer 3D » Mon Jan 11, 2021 11:30 am

5I.3 In a gas-phase equilibrium mixture of H2, I2, and HI at 500. K, (HI)=2.21×10^−3 mol⋅L−1 and [I2]=1.46×10^−3 mol⋅L−1. Given the value of the equilibrium constant in Table 5G.2, calculate the equilibrium molar concentration of H2.

I keep getting 4.21 x 10^-6 mol/L for the concentration of H2 instead of the textbook answer of 2.1 x 10^-5 mol/L. Can someone tell me where I went wrong? I used 794 as the equilibrium constant.

Andrew Jubintoro 3J
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Re: Textbook 5I.3

Postby Andrew Jubintoro 3J » Mon Jan 11, 2021 11:31 am

The equilibrium constant you used is for T=298K not 500K.

Marisa Gaitan 2D
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Re: Textbook 5I.3

Postby Marisa Gaitan 2D » Mon Jan 11, 2021 11:33 am

The Kc value for this reaction at 500K is actually 160. Carrying out your calculation with this Kc value should get you the right answer. I made this mistake too!

Ria Nawathe 1C
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Re: Textbook 5I.3

Postby Ria Nawathe 1C » Mon Jan 11, 2021 11:33 am

I think you're using the wrong K. I used K=160 for H2 + I2 <---> 2HI @ 500K and I got 2.1 * 10^-5 M. Hope this helps!

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