A solution contains 32.7 g H3PO4 in 455 mL of solution. Calculate its molarity.?

Question

Im not sure wat equation of molarity to use so yeah...

Answer 1

Molarity = moles of solution / L of solution

to find moles, u take ur given 32.7 g and divide it by the molar mass of H3PO4

32.7 x (1 mol H3PO4 / 97.994 g H3PO4) = 0.3337 mol H3PO4

and
convert mL to L
455 mL x ( 1 L / 1000 mL) = .455 L

Molarity = .3337 moles / .455 L
= .733 mol/L

Answer 2

If you aren't sure which equation to use, go back to the definitions:

Concentration = amount/volume (always)

More specifically,

Molarity (concentration mol/L) = moles/volume in L

Moles = mass/(molar mass) (always)

= 372g/(molar mass of H3PO4)

Volume = 455 x 10^-3 L

Now you can substitute and do the arithmetic.

VERY IMPORTANT: you don't need to memorise lots of formulas if you understand the principle.

Answer 3

Mwt=98 so [H3PO4] = 32.7 x1000/ (98 x 455) M