posted by GM on .
1.The equilibrium constant for the oxidation of elemental iron metal, Fe, by oxygen, O2 to form hematite, according to the reaction 2Fe + (3/2)O2 = Fe2O3 is known to have the value K=exp(+68.8) at 1000C. The equilibrium constant for the formation of CO2 from carbon and O2, C + O2 = CO2 at the same temperature is known to be K = exp(+48.90). Is it possible to prepare elemental iron in high yield from hermatite by using carbon (from coke) at 1000C? Justify your answer.
2.Glycolic acid is often used in “facial peels” and has a Ka of 1.5x10^-4. If a movie star is to have a solution of pH 2.1 applied to her face at night, what concentration of glycolic acid solution should be made up (assuming that it is a monoprotic acid, and that it dissolves freely in water)
3.The solubility product for silver (I) chloride is 1.6x10^-10 while that for sliver (I) iodide is 8.5x10^-17. Suppose 5g of AgCl is put in a liter of 0.1M sodium iodide solution. If a solid is eventually isolated, what is it, and how did it form?
4.The Kb of ammonia, NH3, is 1.8x10^-5. What is the pH of a 2.000 millimolar solution of ammonia , to 3 significant digits.
5.A weak monoprotic acid was calculated, using the usual formula for Ka, to give a pH of 7.4 at a certain concentration. The student who did the calculation was puzzled. What would you advice him/her to do?
6.Why is it that biochemists often remember the pKa of weak acids, rather than Ka?
7.If we suppose that Kw = 1.0x10^-14 at 25C, would it be larger or smaller at 100C? What is the value of K for the reaction 8H + 8OH = 8H2O at 25C? Would this value be smaller, or larger, at 100C?
I looked only at #1. Seven prolems per post is six too many. Do you have any idea how long it takes to work and type in the answers? Too long. Most volunteers will not tackle one that takes that long to answer.
If you will note, equation 1 reversed + equation 2 times 3/2 will give you a balanced equation for Fe2O3 + C ==>>??
So K' for equation 1 will be 1/K1
K" for equation 2 will be (K2)3/2
Adding the reverse of equation 1 to equation 2 (times 3/2) will give a K for the reaction of K'*K". A positive K value indicates the spontaneity of the reaction under the conditions shown.
Thank You DrBob222! This answer helped alot!