# Chemistry

Consider the following equilibrium:
PCl3 (g) + Cl2 (g) yields PCl5 (g)
delta H= -92KJ

The concentration of PCl3 at equilibrium may be increased by:

decreasing the temp (think this is it)

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1. I don't think so. Remember that Le Chstelier's Principle says that when a system in equilibrium is disturbed it will shift so as to undo what we've done to it.
When dH is involved I rewrite the equation to make more sense.
PCl3 + Cl2 ==> PCl5 + heat
Now, adding PCl3 makes the system want to use up the added PCl3. How can it do that? By reacting more PCl3 with Cl2 to produce PCl6; i.e., shifting the rxn to the right.
Adding more cl2 will shift to the right.
Adding PCl5 will shift to the left.
Adding heat will make it shift to the left.

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2. Sir, thank you for answering. I thought it was the adding the Cl2, but it was wrong. That is why I went with decreasing the temp, but now knowing that it is wrong as well. I think my only option is the addition of PCl5 (which I meant to put at the top vice Pcl4) I hope I am on the right track.

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3. Adding heat and adding PCl5 is th only way to shift it to the left (or course decreasing PCl3 and Cl2 will shift it to the left also). Decreasing T shifts the reaction to the right (because if we take temperature away the reaction will shift to the right in order to produce more heat).

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