[lewisheather]

I am trying to solve this problem. can you tell me if i did it correctly.

Problem: You have 38.8 grams of K2SO4 and this is dissolved in .1 L of water. What is the molarity of K. MW of K2SO4 is 194.

This is how I solved it:

38.8 g K2SO4/194 g m-1 = .2 moles of K2SO4

.2 moles K2SO4 * 1 mol K / 1 mol K2SO4 = .2 mols of K

the molarity is moles/liter so I divided by .1 L the given amount of fluid.

Hence, .2 molesK/ .1 L = 2M K

Is this correct?

[Borek]

Molar mass of K₂SO₄ is 174, so the final result is wrong - although your approach is correct.

CASC rules

[lewisheather]

OK that makes sense. These were the exact numbers given to me on the test. I was just worried that I was doing the wrong calculation.

I showed my work so hopefully they will see that they messed up on the numbers. Or maybe they did this to see if we were paying attention.

I might be wrong on the formula of K2SO4, I am going off of memory of what I thought the question of the test was.  

I was just worried that I was doing the set up wrong.

Thanks so much for your help.

Heather

[oldddog]

Potassium sulphate dissolves in water according to the equation below;
 K₂SO₄(s) + H₂O ---> 2K⁺(aq) + SO₄^2-(aq)
So for every mole of potassium sulphate that dissolves you get 2 moles of potassium ions in solution.

[Borek]

Oops, did I misread the question again?

[Che-Comp]

38.8 g K2SO4 * (1 mol K2SO4/174 g K2SO4) * (2 mols K/1 mol K2SO4)
= 0.446 mols K

Assume volume occupied by K2SO4(aq) is negligible compared to the volume of water.
0.446 mols K/0.1L =  4.46 mols K/1L solution approx. 4M

I am trying to solve this problem. can you tell me if i did it correctly.

Problem: You have 38.8 grams of K2SO4 and this is dissolved in .1 L of water. What is the molarity of K. MW of K2SO4 is 194.

This is how I solved it:

38.8 g K2SO4/194 g m-1 = .2 moles of K2SO4

.2 moles K2SO4 * 1 mol K / 1 mol K2SO4 = .2 mols of K

the molarity is moles/liter so I divided by .1 L the given amount of fluid.

Hence, .2 molesK/ .1 L = 2M K

Is this correct?