## Clarification for problem G.21?

Darren Nguyen 1F
Posts: 60
Joined: Sat Sep 14, 2019 12:15 am

### Clarification for problem G.21?

We did this during discussion but I didn't understand something. When going from grams to moles, he did 0.500 g K2S / 110.27 g * 2 mol K / 1 mol KCl. What was that 2 mol K per 1 mol KCl part? When do we need to do that?

claudia_1h
Posts: 111
Joined: Fri Aug 09, 2019 12:16 am

### Re: Clarification for problem G.21?

The question is asking about the concentration of potassium ions. So, it is necessary to consider how many moles of potassium ions there are per mole of substance so your answer is calculated correctly and has the correct units. However, there are not 2 mol K per 1 mol KCl, so I'm guessing it was supposed to be 2 mol K per 1 mol K2S, the other substance in the problem.

MMckinney_4H
Posts: 61
Joined: Sat Sep 28, 2019 12:16 am

### Re: Clarification for problem G.21?

2 mol K/ 1 mol compound isn't actually applicable for KCl as there would only be 1 mol K for 1 mol KCl. However for K2S, you would have 2 mol K for each mole of the compound. Likewise there would be 3 mol K for each mole of K3PO4

Fatemah Yacoub 1F
Posts: 114
Joined: Thu Jul 11, 2019 12:16 am

### Re: Clarification for problem G.21?

Basically the problem is asking for the concentration of a specific ion so you just have to remember the ration of the concentration of each specific ion to the ratio of the entire compound.