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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: Melo on August 14, 2020, 01:09:19 AM

Title: General Chemistry practice question
Post by: Melo on August 14, 2020, 01:09:19 AM

I have looked at this question a thousand times but I got it wrong apparently.

I seem to get the hard ones right and overthink the easy questions

Please help?
Q: if 20 mL of pure ethanol is diluted to 50 mL with distilled water, what is the concentration of the prepared ethanol solution?

Thanks

Title: Re: General Chemistry practice question
Post by: Borek on August 14, 2020, 02:38:28 AM

You have to show your attempts at solving the problem to receive help, this is a forum policy.

And please change your nick, unless you want your mailbox to be spammed by bots.

Title: Re: General Chemistry practice question
Post by: AWK on August 14, 2020, 03:02:38 AM

https://wiki2.org/en/Volume_fraction
https://www.chembuddy.com/?left=concentration&right=volume-volume-percentage

Title: Re: General Chemistry practice question
Post by: penta-d on August 18, 2020, 11:05:12 AM

For this specific example, where the final volume is 50 mL, it may help to think about doing the dilution twice so that you end up with 100 mL total volume.

For this type of problem in general, I would search wikipedia for "dilution equation." When using that equation you can use any type of concentration (molarity, grams/L, percent by volume, etc.), but for both concentration and for volume make sure to use consistent units on both right and left sides of the equation.

If neither of these methods works out right for you, then please post your attempts/results here and I am sure you will get plenty of help with it.