The World Health Organization recommends that the maximum allowable concentration of chromium(VI) in drinking water be limited to 0.05 mg/L. If the molar absorptivity of chromium(VI) at 345 nm is 1.5*10³/(M cm), what is the absorbance of a solution that contains 0.050 mg/L in a 10-cm-long cell?

Question

Quizplus · Accepted Answer

First, we need to convert the concentration from mg/L to mol/L. The molecular weight of chromium(VI) is 52 g/mol, so:

0.050 mg/L = 0.050 mg/L x (1 g/1000 mg) x (1 mol/52 g) x (1000 L/1 m3) = 9.6 x 10-10 mol/L

Next, we can calculate the absorbance using the Beer-Lambert law:

A = εcl
where A is the absorbance, ε is the molar absorptivity, c is the concentration in mol/L, and l is the path length in cm.

Plugging in the values we have:

A = (1.5 x 1010 M-1 cm-1) x (9.6 x 10-10 mol/L) x (10 cm) = 0.014

Therefore, the absorbance of the solution is 0.014, which is choice C.

The World Health Organization Recommends That the Maximum Allowable Concentration