100 ppm is 100 parts per million. or in equation form
100 ppm = 100 / 1,000,000 = 0.0001
to solve the mass of NaCl that is needed to be dissolved in water to make 1 g of 100 ppm , is by multiplying the equivalent 100 ppm to the mass of 1
mass nacl = 1g ( 0.0001)
mass nacl = 0.0001 g of nacl is needed to dissolve in water to make 1g solution of 100 ppm