Percentage calculation

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Percentage calculation

Postby gene26 » Apr 13 2017 5:26 am

If I have 500ml 65% A and a 100ml 82% A

How do we prepare 140ml 76% of A by mixing both the above solutions?
gene26
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Re: Percentage calculation

Postby relaxin » Apr 13 2017 9:47 am

Just remember that N1xV1 = N2xV2, where N can be percentage, molarity or normality; V is the volume.

Assuming X ml of the 82% is needed to mix with (140-X) ml of the 65%,

X.82 + (140-X).65 = 140 .76

Solve for X
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Re: Percentage calculation

Postby gene26 » Apr 14 2017 12:51 am

relaxin wrote:Just remember that N1xV1 = N2xV2, where N can be percentage, molarity or normality; V is the volume.


I did try to apply N1V1=N2V2
N1 = X.82 + (140-X).65
N2= .76
V1= ?
V2=140

but I couldn't come up with a equation for N1this seems like a GRE math

when do we use N1/V1 = N2/V2
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Re: Percentage calculation

Postby relaxin » Apr 14 2017 11:02 am

Your N1 is wrong (N is for concentration only). Since there are two solutions with different percentage involved, the total sum of N1V1 of the two solutions will be equal to N2V2 of the final solution.

V1 has different values for each of the original solutions, the sum should be equal to V2.
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