# Using 18% by weight ammonium hydroxide to make 16ppm aqueous solution

Frankenstein19
Thread moved from the technical forums to the schoolwork forums
TL;DR Summary: Used M1V1=M2V2 but am unsure if formula applies

I feel like I could use M1V1=M2V2 but the 18% by weight ammonium hydroxide is confusing me so much.

Density of ammonium hydroxide 18% is 0.926 g/cm3

18%V1=16mg/L*200L

(18mg ammonium/100 mg of total solution) * V1 = 3,200mg ammonium (aq)

(18mg ammonium/100 mg of total solution) * V1 = 3,200mg ammonium (aq)

V1 = 3,200mg ammonium / 18mg ammonium * 100mg of total solution

V1 = 17,777 mg of solution × 1g/1000mg × cm3/0.926g

V1 = 1.91 cm3

Is this correct?

## Answers and Replies

Mentor
You even didn't wrote what is the volume you are trying to prepare - is it 200 L?

No, M1V1=M2V2 is not the right approach. You should not operate with volumes, but with masses.

18 ppm is typically w/w - that is, you want your solution to contain 18*10-6 ammonia by mass.

What is mass of the 200 L of the solution? (with no other data I would use just the density of pure water).

18 ppm of that - how many grams of ammonia required?

How many grams of the 18% solution contain required mass of ammonia?

And finally - convert to the volume.

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