The unit ppm (parts per million) should be numerically equal to the unit of mg/L (milligram per liter). First, we determine the volume of the stock solution in L.
V = (100 mL)(1 L/1000 mL)
V = 0.1 L
Then, the equation that would allow us to determine the value of mass is,
C = m/V
where C is concentration, m is mass, and V is the volume.
Substituting the known values,
2 = m/ 0.1
The value of m from the equation is 0.2.
Answer: 0.2 mg
