When a mixture of a aluminum powder and iron (III) oxide is ignited, it produced molten iron and aluminum oxide. In an experiment, 5.4 gm of aluminium was mixed with 18.5 gm of iron (III) oxide. At th

Question

When a mixture of a aluminum powder and iron (III) oxide is ignited, it produced molten iron and aluminum oxide. In an experiment, 5.4 gm of aluminium was mixed with 18.5 gm of iron (III) oxide. At the end of the reaction, the mixture contained 11.2 gm of iron, 10.2 gm of aluminum oxide, and an undetermined amount of unreacted iron (III) oxide. No aluminum was left. If the mass of the iron (III) oxide left was ' X ' gm, then find the value of [ X + 2.5 ]

TestHub · Accepted Answer

Question Explanation: Apply mass conservation to find unreacted reagent mass.

Concept: Law of Conservation of Mass.

Solution: In the thermite reaction, the total mass of reactants must equal the total mass of all products plus any unreacted material. We subtract the mass of produced iron and aluminum oxide from the initial mixture mass to find unreacted $Fe_{2} O_{3}$ .

$2 Al + Fe_{2} O_{3} \to Al_{2} O_{3} + 2 Fe_{(s)}$

$5.4 gm 18.5 gm 10.2 gm 11.2 gm$

Initial mass $= 18.5 + 5.4 = 23.9 gm$

Weight of product $= 10.2 + 11.2 = 21.4 gm$

Mass of unreacted $Fe_{2} O_{3} = 2.5 gm$

Final answer: 5

Chemistry - Stoichiometry Question with Solution | TestHub

Doubts & Discussion