Asked by Ken

Cola drinks have a phosphoric acid content that is described as `from 0.057% to 0.084% of 75% phosphoric acid, by mass." Estimate the pH range of cola drinks corresponding to this average range of H3PO4 content.

I am having trouble with the wording of this question, I know I need to find the mass first, then the analytical concentration of H3PO4, but I have no idea how.
Answered by DrBob222
I agree it is a little confusing as to exactly what they want. In particular the pH range of the average range is confusing but I would go with the average percent or (0.057+0.084)/2 = about 0.0705%. I would start with 100 mL of solution and that will contain 100 x 0.000705 = 0.0705g of H3PO4. Since that is only 75% pure, then g actual H3PO4 is
0.0705 x 0.75 = g H3PO4.
Convert that to mols, then M = mols/0.1L = ?
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