Answer
0.857 M
Work Step by Step
Let the volume of the solution be 1 L.
$\text{Mass of the solution}=\text{Density}\times\text{Volume}$
$=1.007\, g/mL\times1000\, mL=1007\,g$
$\text{Mass of ascetic acid}=1007\,g\times\frac{5.11}{100}$
$=51.4577\, g$
$\text{Moles of ascetic acid}=\frac{51.4577\,g}{60.052\,g/mol}$
$=0.857\, mol$
$\text{Molarity}=\frac{\text{Moles of solute}}{\text{Volume of solution in L}}$
$=\frac{0.857\,mol}{1\,L}=0.857\,M$