Question

How many moles of H3PO4 does a 125-g sample of a phosphoric acid solution that is 85.5% H3PO4 by mass contain

Answer 1

85.5% means that there are 85.5 grams of \(H_3PO_4\) in 100 grams of solution.

so if you have 125 g of solution, 125 g* 0.855= \(m_{H_3PO_4}\)

to find moles you would divide this number by the molar mass of \(H_3PO_4\)

the formula is: \(n=\dfrac{m}{M}\)

n=moles
m=mass
M=molar mass