Calcium levels in blood can be determined by adding oxalate...

Calcium levels in blood can be determined by adding oxalate ion to precipitate calcium oxalate, $\mathrm{CaC}_{2} \mathrm{O}_{4},$ followed by dissolving the precipitate in aqueous acid and titrating the resulting oxalic acid $\left(\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\right)$ with $\mathrm{KMnO}_{4}$ $$\begin{aligned} 5 \mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}(a q)+2 \mathrm{MnO}_{4}^{-}(a q)+6 \mathrm{H}^{+}(a q) \longrightarrow & \\ & 10 \mathrm{CO}_{2}(g)+2 \mathrm{Mn}^{2+}(a q)+8 \mathrm{H}_{2} \mathrm{O}(l) \end{aligned}$$ How many milligrams of $\mathrm{Ca}^{2+}$ are present in 10.0 $\mathrm{mL}$ of blood if 21.08 $\mathrm{mL}$ of 0.000988 $\mathrm{M} \mathrm{M} \mathrm{MnO}_{4}$ solution is needed for the titration?

Calcium levels in blood can be determined by adding oxalate ion to precipitate calcium oxalate, $\mathrm{CaC}_{2} \mathrm{O}_{4},$ followed by dissolving the precipitate in aqueous acid and titrating the resulting oxalic acid $\left(\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\right)$ with $\mathrm{KMnO}_{4}$
$$\begin{aligned} 5 \mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}(a q)+2 \mathrm{MnO}_{4}^{-}(a q)+6 \mathrm{H}^{+}(a q) \longrightarrow & \\ & 10 \mathrm{CO}_{2}(g)+2 \mathrm{Mn}^{2+}(a q)+8 \mathrm{H}_{2} \mathrm{O}(l) \end{aligned}$$
How many milligrams of $\mathrm{Ca}^{2+}$ are present in 10.0 $\mathrm{mL}$ of blood if 21.08 $\mathrm{mL}$ of 0.000988 $\mathrm{M} \mathrm{M} \mathrm{MnO}_{4}$ solution is needed for the titration?

Key Concepts

Precipitation Reaction

A precipitation reaction is one in which two soluble ions combine in solution to form an insoluble solid, known as a precipitate. This concept is utilized in analyses to selectively remove or measure certain ions from a mixture by inducing the formation of a precipitate, which can then be separated and analyzed further.

Molarity and Concentration Calculations

Molarity, defined as the number of moles of solute per liter of solution, is a fundamental concept for quantifying concentrations in solutions. It allows for calculations that convert between the volume of a solution and the number of moles of a substance, linking experimental measurements like titrant volume to the amount of analyte present.

Stoichiometry

Stoichiometry involves using the balanced chemical equation to determine the quantitative relationships between reactants and products in a chemical reaction. This concept allows one to deduce how many moles of one substance react with or produce a given number of moles of another substance, which is crucial when linking titration data to the amount of analyte present.

Redox Titration

Redox titration is a method of chemical analysis that relies on a redox reaction between the titrant and the analyte. In this type of titration, an oxidizing agent (or reducing agent) reacts with the substance being analyzed, and the amount of titrant required to complete the reaction is used to determine the concentration or amount of the analyte. Its application requires a clear understanding of the electron transfer that occurs in the reaction.

Mass-Mole Conversion

Mass-mole conversion is a critical technique in analytical chemistry, where it is necessary to convert the moles of a substance calculated from titration or other methods into its mass. This process involves using the molar mass of the compound and is essential for reporting results in practical units such as grams or milligrams.

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