find molar concentration of the solution.

.128 g of benzophenone and fill in a beaker with ethanol to the 50.00mL line

i came up with 3.5 x 10^-5

(0.128)(1/182.217)(.049872)

M = mols/L

mols = 0.128/182.217 which is OK.
But the divisor should be 0.050 and not 0.049872. Molarity is mols per liter OF SOLUTION.