August 08, 2022, 04:23:48 AM
Forum Rules: Read This Before Posting

0 Members and 1 Guest are viewing this topic.

Smileylover1

• New Member
• Posts: 4
• Mole Snacks: +0/-0
Question about mass percentage in a mixture
« 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

Borek

• Mr. pH
• Deity Member
• Posts: 27142
• Mole Snacks: +1762/-405
• Gender:
• I am known to be occasionally wrong.
Re: Question about mass percentage in a mixture
« Reply #1 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)
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

Corribus

• Chemist
• Sr. Member
• Posts: 3348
• Mole Snacks: +505/-23
• Gender:
• A lover of spectroscopy and chocolate.
Re: Question about mass percentage in a mixture
« Reply #2 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.
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

Borek

• Mr. pH
• Deity Member
• Posts: 27142
• Mole Snacks: +1762/-405
• Gender:
• I am known to be occasionally wrong.
Re: Question about mass percentage in a mixture
« Reply #3 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
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

Smileylover1

• New Member
• Posts: 4
• Mole Snacks: +0/-0
Re: Question about mass percentage in a mixture
« Reply #4 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

Smileylover1

• New Member
• Posts: 4
• Mole Snacks: +0/-0
Re: Question about mass percentage in a mixture
« Reply #5 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