Homework 11.13 Reaction Quotient Q

[Feng Ming Li 2K]

Write the reaction quotient Q for
(a) 2 BCl3(g) + 2 Hg(l) ---> B2Cl4(s) + Hg2Cl2(s)
(b) P4S10(s) + 16 H2O(l) ---> 4 H3PO4(aq) + 10 H2S(aq)
(c) Br2(g) + 3 F2(g) ---> 2 BrF3(g)

If I use the formula in the book which is Q= [Products]/[Reactants]. I would get a different answer from what is shown in the solutions manual. For part (a), why is the answer Q=1/[P BCl3]^2 ? For part (b), how come the answer is [H3 PO4]^4 [H2S]^10 ? What happened to the reactants?

[Juliana Nghiem 3G]

Hi! When finding the reaction quotient Q, even though it's [products]/[reactants], we still have to remember that we do not take into account solids and liquids. Since for part a, Hg is a liquid and B2Cl4 as well as Hg2Cl2 are solids, we don't take them into the equation, leaving it as 1/(P BCl3)^2.

Same for part b, since P4S10 is a solid and H2O is a liquid, we don't them them into the consideration for the reaction quotient, leaving the answer as [H3PO4]^4 [H2S]^10.

Hope this helped!

[Sable Summerfield]

What do we not put a P in front of the answer for (b)?