Question

Oxalic acid ${H_2}{C_2}{O_4}$ is present in many plants and vegetables. If 24.0 mL of 0.01M $KMn{O_4}$ solution is needed to titrate 1.0 g of ${H_2}{C_2}{O_4}$ to equivalence point, the mass percentage (as nearest integer) of ${H_2}{C_2}{O_4}$ in the sample is:

Answer 1

Hint: Equivalence point: point in titration at which the amount of titrant added is just enough to completely neutralize the analyte solution. At the equivalence point in an acid-base titration, moles of base = moles of acid and the solution only contains salt and water.

Complete Step by step answer:Mass percentage is one way of representing the concentration of an element in a compound or a component in a mixture. Mass percentage is calculated as the mass of a component divided by the total mass of the mixture, multiplied by 100%.
Number of moles $KMn{O_4}$ = $\dfrac{{volume}}{{1000}} \times molarity$
Here, we are given with volume =24.0mL and molarity =0.01.
Number of moles $KMn{O_4}$= $\dfrac{{24.0}}{{1000}} \times 0.01 = 0.00024mol.$
 2 moles of $KMn{O_4}$ = 5 moles of ${H_2}{C_2}{O_4}$
So 1 moles of$KMn{O_4}$ =$\dfrac{5}{2}$ moles of ${H_2}{C_2}{O_4}$and therefore 0.00024 moles of$KMn{O_4}$ = $\dfrac{5}{2} \times 0.00024 = 0.0006mol$ of ${H_2}{C_2}{O_4}$.
Number of moles of ${H_2}{C_2}{O_4}$ =$\dfrac{5}{2} \times 0.00024 = 0.0006mol$
Mass of ${H_2}{C_2}{O_4}$ = $mass = molar\;mass \times moles$ (Molar mass of oxalic acid = 90 g/mol. And
moles = 0.0006.) $mass = 0.0006 \times 90 = 0.054g$.
Mass percent is the mass of the element or solute divided by the mass of the compound or solute. The result is multiplied by 100 to give a percent.
The formula for the amount of an element in a compound is:
mass percent = (mass of element in 1 mole of compound / mass of 1 mole of compound) x 100
Mass percentage of ${H_2}{C_2}{O_4}$= $\dfrac{{0.054}}{1} \times 100 = 5.4\% $

The nearest integer is 5.

Note: The main difference between equivalence and endpoint is that the equivalence point is a point where the chemical reaction comes to an end while the endpoint is the point where the color change occurs in a system.