Question

A method to measure soluble organic carbon in seawater includes oxidation of the organic materials to CO₂ with K₂S₂O₈, followed by gravimetric determination of the CO₂ trapped by a column 0f Ascarite. A water sample weighing 6.234 g produced 2.378 mg of CO₂(FM 44.009). Calculate the ppm carbon in the seawater.

Short answer

the ppm carbon in the seawater is 104.1.

Step-by-step solution

Calculate the moles of CO2:

In this task we have a water sample of 6.234 g which produced 2.378 mg of CO₂(M=44.009 g/mol). Here we will calculate the ppm of carbon in the seawater.

Calculating the moles of CO_2:

$$\begin{gathered} \mathrm{n}\left({\mathrm{CO}}_2\right)=\frac{\mathrm{m}}{\mathrm{M}} \\ \mathrm{n}\left({\mathrm{CO}}_2\right)=\frac{2.378\mathrm{mg}}{44.010\mathrm{g}/\mathrm{mol}} \\ \mathrm{n}\left({\mathrm{CO}}_2\right)=5.4033\times {10}^{-5}\mathrm{mol} \end{gathered}$$

Consider that $\mathrm{n}\left({\mathrm{CO}}_2\right)=\mathrm{n}\left(\mathrm{C}\right)$.

Calculate the mass and ppm of Carbon (C):

Mass of carbon (C) is,

$$\begin{gathered} \mathrm{m}\left(\mathrm{C}\right)=\mathrm{n}\times \mathrm{M} \\ \mathrm{m}\left(\mathrm{C}\right)=(5.4033\times {10}^{-5})\mathrm{mol})\times 12.01\mathrm{g}/\mathrm{mol} \\ \mathrm{m}(\mathrm{C})=6.49\times {10}^{-4}\mathrm{g} \end{gathered}$$

Ppm of carbon in the seawater is,