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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: Smileylover1 on April 29, 2022, 11:21:50 AM

Title: Question about mass percentage in a mixture
Post by: Smileylover1 on April 29, 2022, 11:21:50 AM
Hello,
There's this one problem I'm having quite a lot of trouble with.
I know that to solve it, you have to find out the 'amount' (coefficients) of each compound in the mixture, but I honestly have no clue on how to do that.

The question goes as follows:

There's a mixture containing K2S, K2SO3 and K2SO4 (unequal amounts of each compound)
The m% of K is 60,0%
How much O is present in this mixture?


Any help would be greatly appreciated, thanks
Title: Re: Question about mass percentage in a mixture
Post by: Borek on April 29, 2022, 11:34:27 AM
If there is 60% of K, can you calculate how much S is present?

(hint: compare all formulas)
Title: Re: Question about mass percentage in a mixture
Post by: Corribus on April 29, 2022, 11:37:36 AM
It is also sometimes helpful in problems like this to just assume a certain mass of mixture, like 100 g. Working with absolute masses can be more intuitive than working with mixture %'s. You can then convert back to a % at the end.
Title: Re: Question about mass percentage in a mixture
Post by: Borek on April 29, 2022, 03:26:27 PM
It is also sometimes helpful in problems like this to just assume a certain mass of mixture, like 100 g.

That's my standard advice, but in this particular question it is probably not the most important thing :)
Title: Re: Question about mass percentage in a mixture
Post by: Smileylover1 on April 29, 2022, 05:29:42 PM
It is also sometimes helpful in problems like this to just assume a certain mass of mixture, like 100 g. Working with absolute masses can be more intuitive than working with mixture %'s. You can then convert back to a % at the end.

Thank you so much! This lead to a break-through

using n=m/M and 100g, and the amount of moles of S being 1/2 of those of K, it worked :)

Title: Re: Question about mass percentage in a mixture
Post by: Smileylover1 on April 29, 2022, 05:30:13 PM
If there is 60% of K, can you calculate how much S is present?

(hint: compare all formulas)

Thank you for the comment, along with another one it helped me find the solution :)