Finding out moles.?

Question

In this equation, H3PO4+3NaOH-->Na3PO4+3H2O, I have to find out how much NA3PO4 can be prepared by the reaction of 4.7g of H3PO4 w/ an excess of NaOH.
How do I know how many moles I have to start the conversion factors?

Answer 1

H3PO4 + 3NaOH -> Na3Po4 + 3H2O
4.7g
x mol

To find how many moles of H3PO4 you need, take the mass of H3PO4 you have and divide it by its relative molecular mass.

Hence,

Mr of H3PO4 = 3(1) + (31) + 4(16) = 98

n(H3PO4) = 4.7 / 98 = 0.048 mol.

Answer 2

convert 4.7g to moles of H3PO4