ppm or part er million is used to measure the concentration of solute in a given volume of solution.
We can calculate it by the formula
[tex]ppm=\frac{mass\text{ of solute \lparen in mg\rparen}}{Volume\text{ of solution \lparen in L\rparen}}_[/tex]In our question we have the next data:
*Mass of methanol
[tex]1.56\text{ }\times10^{\frac{-}{}5}g=1.56\times10^{-2}mg[/tex]where we have to convert from g to mg.
* The volume of the solution is:
[tex]250\text{ ml = 0.250 L}[/tex]where we have to convert from ml to L
Putin the values on the right-hand side of the equations above we get:
[tex]ppm=\frac{1.56\times10^{-5}mg}{0.250\text{ L}}=0.0624[/tex]Looking at the option in the question, by similarity we chose the option c, that is , we chose ppm=0.0611
