Question

A student reported the following composition of an unknown mixture, 25% NH4Cl, 30% NaCl, and 50% SiO2. Assuming the student's calculations are correct, explain the error.

Answer 1

Answer: The composition of the unknown mixture is more than 100 %, which is not possible.

Step-by-step explanation:

Composition of a mixture is defined as the sum of the amount of substances that are present in the mixture. The maximum composition of a mixture can be 100 %

We are given:

Composition of ammonium chloride in the mixture = 25 %

Composition of sodium chloride in the mixture = 30 %

Composition of silicon oxide in the mixture = 50 %

Composition of mixture = (25 + 30 + 50) = 105 %

As, the measured value of unknown mixture is more than the true value which is 100 %. Thus, the error lies here only.

Hence, the composition of the unknown mixture is more than 100 %, which is not possible.

Answer 2

The three substances add up to 105% instead of 100%. Also, the amount of either one of those compounds is more than according to the Stoichiometry of the reaction, meaning one of those compounds is in excess.