The first step is to convert the volume of solution in mililiters to liters, use a conversion factor to do it:
[tex]100mL\cdot\frac{1L}{1000mL}=0.1mL[/tex]Now, multiply the volume of the solution by its concentration to find the number of moles that are needed to make that solution (remember that M=mol/L):
[tex]0.1L\cdot\frac{0.2mol}{L}=0.02mol[/tex]Finally, convert this amount of moles to grams using the molecular weight of K2CrO4 (MW=194.2g/mol):
[tex]0.02mol\cdot\frac{194.2g}{mol}=3.884g[/tex]The amount of grams of K2CrO4 to make 100ml of solution is 3.884g.
