Applications of Equilibrium Constants

[erok81]

Homework Statement

At 1285*C the equilibrium constant for the reaction $$Br_2 (g) \Leftrightarrow 2Br (g)$$. A 0.200L vessel containing an equilibrium mixture of the gasses has 0.245g of $$Br_2$$(g) in it. What is the mass of Br(g) in the vessel?

Homework Equations

None

The Attempt at a Solution

I have tried this 4-5 different ways at least and cannot get close to the answer. I started with this

$$K_c = \frac{[Br]^{2}}{[Br_2]}$$

Rearrange that to solve for Br. I get...

$$[Br_2] \times K_c = [Br]^2$$

Then after that I am lost. I've tried converting Br_2 from grams to moles. Leaving it as grams and converting at the end. The answer in the book is in M, but I cannot even come close to that.

Any hints? I know for sure just plugging in grams of Br_2 and K_c, then solving for x doesn't get me even in the ballpark.

The book answer is 0.00767M. Which strangly enough is what I get what I convert 0.245g of Br_2 into M.

The answer I get at the end is 0.0028 M Br.



EDIT! Nevermind. I am a moron. I had the answer right the whole time I just wasn't reading the answer book correctly.

 

[nate808]

I understand your frustration in trying to solve this problem. However, it seems like you have already solved it correctly and the answer in the book matches your calculation. It is possible that you misread the answer in the book or made a small calculation error. I would suggest double-checking your calculations and trying it again. If you are still having trouble, feel free to ask for assistance from your classmates or your instructor. Remember, it's always helpful to have a second pair of eyes on a problem.

Additionally, it's important to understand the concept behind the equilibrium constant and how it relates to the concentrations of the reactants and products. Perhaps reviewing this concept and practicing some more problems will help solidify your understanding.

Best of luck with your studies. Keep up the good work!

 

[Blueshift5]

it is important to carefully read the question and understand the units being used. In this case, the question is asking for the mass of Br(g) in the vessel, not the concentration. The equilibrium constant and the given amount of Br_2 can be used to calculate the moles of Br_2 present in the vessel. Since the reaction is in a 0.200L vessel, the concentration of Br_2 can then be calculated and converted to moles of Br. Finally, using the molar mass of Br, the mass of Br(g) in the vessel can be determined. It is important to pay attention to units and carefully convert between them to ensure accurate calculations.