Answer: 0.285 mol Se
Explanation:
By looking at the periodic table we can determine that the molar mass of Selenium is 78.963 g/mol. In order to determine the moles of Selenium, all we have to do is take the mass (22.5 g) and divide by the molar mass (in g/mol) so that grams cancel out and we are left with moles.
\(22.5g*\frac{1mol} {78.963g}=0.285 mol\)
