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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: pinkglitter07 on April 17, 2006, 04:08:18 PM

Title: How do I calculate the number of moles of H2O present at equilibrium?
Post by: pinkglitter07 on April 17, 2006, 04:08:18 PM

Here's the question I am having problems with:

2NaHCO3 (s) goes to Na2CO3 (s) + H20 (g) + CO2 (g)
A sample of 100. grams of solid NaHCO3 was placed in a previously evacuated rigid 5.00-liter container and heated to 160 C. Some of the original solid remained and the total pressure in the container was 7.76 atmospheres when equilibrium was reached. Calculate the number of moles of H20 (g) present at equilibrium.

I started this problem like the other equilibrium problems I have done, and made a chart with initial, change, and equilibrium. Once I found the X's however, I realized that I had to K. Then I wasn't sure how to calculate K- NaHCO3 is a solid. I'm really confused and don't know how to work with the pressure and moles as well as the solids. Any help would be greatly appreciated!!

Title: Re: How do I calculate the number of moles of H2O present at equilibrium?
Post by: Borek on April 17, 2006, 05:59:15 PM

Activity of solid = 1, but you don't need K.

What gases are present in the container at 160 deg C?