Question

the density of pure water is 1 g/ml. when doing ppm and ppb calculations, we assume 1 l of solution weighs 1 kg. this means that we assume that the density of the solution is 1 g/ml. why are we allowed to make this assumption?

Answer 1

A 5.0-g sample of spinal fluid contains 3.75 mg (0.00375 g) of glucose. What is the percent by mass of glucose in spinal fluid?

Solution

The spinal fluid sample contains roughly 4 mg of glucose in 5000 mg of fluid, so the mass fraction of glucose should be a bit less than one part in 1000, or about 0.1%. Substituting the given masses into the equation defining mass percentage yields:

%glucose=3.75mgglucose×1g1000mg5.0gspinalfluid=0.075%(8.3.2)

The computed mass percentage agrees with our rough estimate (it’s a bit less than 0.1%).

Step-by-step explanation: