It's a mole fraction problem and it's very similar to a fraction problem in math. In math, for example, if you have 4 apples and 6 oranges, the fraction of apples is 4/10 (number apples over total fruit) and the fraction of oranges is 6/10. In mols it's the same thing.
I must say that the problem is not worded very well. There are two way for me to interpret the problem.
1. The author of the problem expects you to ignore the water. In that case, you have 1.218 mols Ca ions and 0.943 mols Li ions. total ions is 2.161 so mole fraction (that's X) is
XCa ions = 1.218/2.161 - ? and XLi ions = 0.943/2.161 - ?
2. Technically, one can't ignore the water BUT the problem doesn't tell you how much water is there. (Yes, the solution is 500 mL but that isn't the amount of water because the Li and Ca ions take up some room too.) If we ignore that and say we have 500 mL H2O, that weighs 500 grams the mols H2O = grams/molar mass = 27.778 mols.
Then total mols is 1.218 + 0.943 + 27.778 = ? and
XCa ions = 1.218/total mols = ?
etc.
My guess is that the author plans for you to ignore the water. If that's so it's an error. If the author expects you to include the water, it's an error, also, because the amount of water can be estimated only.
Hope I've not confused you with all the hype.
You have combined 1.218 moles of calcium ions and 0.943 moles of lithium ions in enough solvent to make 500.00mL of solution. What is the mole fraction of lithium ions in this solution?
What type of problem is this and how do I set it up to solve?
2 answers
No Thank you very much.
1 answer