Question

What is the concentration of O2(g), in parts per million, in a solution that contains 0.008 gram of O2(g) dissolved in 1000. grams of H2O(l)?

Answer 1

concentration of O₂ dissolved in H₂O can be written as ppm

ppm stands for parts per million - mg/kg

the amount of mg in 1 kg of solution

the mass of O₂ - 0.008 g

1000 mg equivalent to 1 g

therefore mass of O₂ in mg - 0.008 g x 1000 mg/g = 8 mg

the mass of water is 1000 g

1000 g is equivalent to 1 kg

mass of water in kg - 1000 g / 1000 g/kg = 1 kg

there's 8 mg of O₂ in 1 kg of water

therefore concentration of O₂ is - 8 mg/kg

also can be written as 8 ppm

answer is 8 ppm

Answer 2

Answer : The concentration of $O2(g)$ in parts per million is, 8 ppm

Solution : Given,

Mass of oxygen gas (solute) = 0.008 g

Mass of water (solvent) = 1000 g

First we have to calculate the mass of solution.

Mass of solution = Mass of solute + Mass of solvent = 0.008 + 1000 = 1000.008 g

Now we have to calculate the concentration of $O2(g)$ in parts per million.

ppm : It is defined as the mass of solute present in one million $(10^6)$ parts by mass of the solution.

$ppm=\frac{\text{Mass of solute}}{\text{Mass of solution}}\times 10^6$

Now put all the given values in this expression, we get

$ppm=\frac{0.008g}{1000.008g}\times 10^6=7.99=8ppm$

Therefore, the concentration of $O2(g)$ in parts per million is, 8 ppm