How many grams of lactic acid (C3H6O3 3,6,3 are subscripts) are in a .5M solution of lactic acid?

Question

The masses are 12 for C 1 for H and 16 for O.

PLEASE also explain how to solve it

Answer 1

The molar mass of lactic acid is roughly 90.09.  So, in a half molar solution, you'd have 45.05 grams of lactic acid.

Find the molar mass.

Multiply by the Molarity of the solution.

Answer 2

First calculate the molecular weight of lactic acid. Also, you must assume a volume, let's use 1 L.

C x 3 = 12 x 3 = 36

H x 6 =  1 x 6 = 6

O x 3 = 16 x 3 = 48

36 + 6 + 48 = 90 g / mole

moles C3H6O3 = M C3H6O3 x L C3H6O3 = (0.5)(1) = 0.5 moles

0.5 moles C3H6O3 x (90 g C3H6O3 / 1 mole C3H6O3) = 45 g C3H6O3 in 1L of 0.5 M solution

Answer 3

0.5 M lactic acid contains 0.5 moles of lactic acid in 1 liter of solution.

0.5 moles x 90 g/mole = 45 g per liter

(90 is the molar mass of C3H6O3; 3x12 + 6x1 + 3x16 = 90 g/mole)

liters x 45 g/liter = grams

If you have 336 mL (0.336 L) the solution contains 15.13 g lactic acid (0.336 x 45 g/l = 15.12 g; 15 g)