Multiple choice

A sample of sea water contains $5\times 10^{-3}g$ of dissolved oxygen in $1\ kg$ of the sample. The concentration of $O_{2}$ in that sea water sample in ppm is:

  1. $5\times 10^{4}$
  2. $5\times 10^{-3}$
  3. $5\times 10^{-2}$
  4. $5\times 10^{-1}$
  5. $5$
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E Correct answer
Explanation

Concentration in ppm is defined as (mass of solute / mass of solution) * 10^6. Here, mass of solute = 5 * 10^-3 g and mass of solution = 1 kg = 1000 g. Thus, (5 * 10^-3 / 1000) * 10^6 = 5 * 10^-3 * 10^3 = 5 ppm.

AI explanation

The concentration in parts per million is calculated as the mass of the solute divided by the mass of the solution, multiplied by $10^6$. Here, $1$ kg is equivalent to $10^6$ mg, making the proportion $5 * 10^{-3} g$ per $1000$ g. The concentration is $(5 * 10^{-3} / 1) * 10^6 = 5$ ppm.

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