Question

the use of parts per million (ppm) and parts per billion (ppb) allows for the conversion of very small concentrations of solute into more comprehensible normalized numbers. using the equation for parts per billion, calculate the levels of cadmium in a 1.00 l sample of water containing 0.005 mg of cadmium. to calculate the mass of the sample assume a density of 1.0 g/ml. $ppb=\frac{mass solute}{mass solution}\times10^{9} ppb$ 50 ppb 5 ppb 0.5 ppb 500 ppb

Explanation:

Step1: Calculate mass of solution

Given volume $V = 1.00\ L=1000\ mL$, density $
ho = 1.0\ g/mL$. Using $m=
ho V$, we have $m = 1.0\ g/mL\times1000\ mL = 1000\ g=10^{6}\ mg$.

Step2: Calculate ppb

Mass of solute $m_{solute}=0.005\ mg$, mass of solution $m_{solution}=10^{6}\ mg$. Using the formula $ppb=\frac{m_{solute}}{m_{solution}}\times 10^{9}$, we get $ppb=\frac{0.005\ mg}{10^{6}\ mg}\times10^{9}= 5\ ppb$.

Answer:

5 ppb