Toxic chemicals in drinking water usually are reported and a safety level specified in units of parts per million (ppm) by mass. What is the molar concentration of arsenic in a water sample that has 1ppm arsenic (As)?
1 ppm = 1 mg/L and although that isn't by mass at 1 ppm by mass and by volume is essentially the same.
So you have 1 mg/L
Convert 1 mg to mols As.
To find the molar concentration of arsenic in a water sample that has 1 ppm (parts per million) of arsenic, we need to know the molar mass of arsenic.
The molar mass of arsenic (As) is approximately 74.92160 grams per mole (g/mol).
To convert the mass concentration (1 ppm) to molar concentration, we need to divide by the molar mass.
First, let's convert 1 ppm to grams.
1 ppm means 1 gram of arsenic in 1 million grams of water.
So, 1 ppm of arsenic is equivalent to 1 gram of arsenic in 1 million grams of water.
Next, we divide the mass of arsenic (1 gram) by the molar mass of arsenic (74.92160 g/mol) to get the number of moles:
1 gram / 74.92160 g/mol = 0.0133408 moles
Thus, the molar concentration of arsenic in the water sample with 1 ppm arsenic is approximately 0.01334 moles per liter (mol/L), assuming the density of water is 1 g/mL.
Remember, ppm is a mass concentration unit, so the molar concentration will depend on the molar mass of the substance you are calculating it for.