Question

A sea water sample contains $7\times {10}^{-3}\text{g}$ of dissolved oxygen per kilogram. Calculate the concentration of oxygen in $\text{ppb}$?

• A. $7\text{ppb}$
• B. $7\times {10}^{-3}\text{ppb}$
• C. $7000\text{ppb}$
• D. $700\text{ppb}$

Answer 1

The correct option is C $7000\text{ppb}$

$1000\text{g}$ of sea water contains $7\times {10}^{-3}\text{g}$ of oxygen.
Concentration in $\text{ppb}$ $=\frac{\text{Mass of solute}}{\text{Mass of solution}}\times {10}^9=\frac{7\times {10}^{-3}}{{10}^3}\times {10}^9=7000$