Question

Determine the concentrations of K2SO4, K , and SO42– in a solution prepared by dissolving 2.84 × 10–4 g K2SO4 in 2.25 L of water. Express all three concentrations in molarity. Additionally, express the concentrations of the ionic species in parts per million (ppm). Note: Determine the formal concentration of SO42–. Ignore any reactions with water.

Answer 1

2.84-4g/about 175 = about 1.62E-6
and 1.62E-6/2.25 = 7.2E-7 M
.......K2SO4 ==> 2K^+ + SO4^2-
I......7.2E-7M....0......0
C.....-7.2E-7..2*7.2E-7M..7.2E-7M
E.......you can fill this in.

The easy way to convert to ppm is to calculate the number of mg/L. For example, for 7.2E-7 (sulfate):
g SO4 = 7.2E-7 mol/L x (96 g/mol) = 6.9E-5 g/L and that is 6.9E-2 mg/L = 0.069 ppm.
Check my work.

Answer 2

I don't understand

Answer 3

You need to do better than that. You have a page and a half of work and you don't understand. That doesn't tell me anything. I have to know where to start. What don't you understand. Exactly and detailed.

Answer 4

I don't understand it at all from the beginning. I get that you divided moles by molar mass for the first thing but I don't know what you did after that. And would I do the same for the rest of the question as well? K2SO4, K+, SO4..I think it would help me if you could do just a part of the problem step by step. I do however understand how I can convert to ppm so thank you for that!

Answer 5

Perhaps I just put in too much stuff. K2SO4 is an ionic compound and it dissolves in water to produce 2K^+ and SO4^2-. If the molarity of K2SO4 is 7.2E-7 M, then that must be the concn of the SO4^2- and twice that must be the concn of the K^+ (since there are 2 K^+ per molecule K2sO4. I just put all of that information in the form of an ICE chart.

Answer 6

Thank you so much! I understand it now! I don't know what the ICE chart is so I didn't know what you were doing. But thank you!

Answer 7

I like the ICE chart and I learned to make ICE charts by volunteering to do this homework help. The I stands for initial, the C for change, and the E for equilibrium. It is a very good way to sum up a problem with initial, change, and equilibrium, and many teachers around the country are using this technique.