Answer
$26.8\;M\;Zn$
Work Step by Step
For ease of calculation, we will assume that there is 100 g of sample. Recall that molarity is mol solute / L solution.
First, find moles of Zn present (molar mass = 65.38 g/mol).
$100\;g\times20.0\%\;Zn=20.0\;g\;Zn$
$\frac{20.0\;g}{}(\frac{1\;mol}{65.38\;g})=0.306\;mol\;Zn$
Next, find volume of solution using the given density:
$8750\;kg/m^3=8750\;kg/(1000\;L)=8.750\;kg/L$
$\frac{100\;g\;sample}{}(\frac{1\;kg}{1000\;g})(\frac{1\;L}{8.750\;kg})=0.0114\;L\;solution$
Next, calculate molarity:
$\frac{0.306\;mol\;Zn}{0.0114\;L\;solution}=26.8\;M\;Zn$
