Question

How much quantity of zinc in grams will have to be reacted with excess dilute HCl solution to produce sufficient hydrogen gas for completely reacting with the oxygen obtained by decomposing potassium chlorate?
A. 12
B. 45
C. 5
D. 7.85

Answer 1

Mole is a SI unit for measuring the quantity of the substance. It can be obtained by dividing the mass of the solution by its molecular weight. Molecular weight can be calculated as adding individual atomic weight present in the molecule.

Complete step by step answer:
The decomposition of potassium chlorate can be written as follows,
$2KCl{O_3} \to 2KCl + 3{O_2}$
From the above equation, it is clear that 2 moles of $KCl{O_3}$ decomposing to give 3 moles of ${O_2}$
Thus, 1 mole of $KCl{O_3}$ decomposing to give $\dfrac{3}{2}$ mole of ${O_2}$
1 mole of $KCl{O_3}$ can be calculated by using the mole formula.
$Mole = \dfrac{{Wt}}{{Mol.wt}}$
$Mole = \dfrac{{5.104g}}{{122.5g/mol}}$
$= 0.0417mol$
$KCl{O_3}$ contains $0.0417mol$. It is known that 1 mole of $KCl{O_3}$ decomposing to give $\dfrac{3}{2}$ mole of ${O_2}$
Thus, 1 mole of oxygen can be calculated as
$Mole = \dfrac{3}{2} \times 0.0417mol$
$= 0.063mol$
The balanced reaction for reacting oxygen and hydrogen molecule can be written as,
$2{H_2} + {O_2} \to 2{H_2}O$
From the above equation, it is clear that two moles of hydrogen reacts with 1 mole of oxygen molecules. Thus, 1mole of hydrogen molecule can be calculated as,
$Mole = 2 \times 0.063$
$= 0.126mol$
Thus, hydrogen molecule contains $0.126mol$
When zinc reacts with an excess of dilute HCl, it forms zinc chloride. The balanced chemical reaction can be written as,
$Zn + 2HCl \to ZnC{l_2} + {H_2}$
From the above equation, it is clear that 1 mole of zinc gives 1 mole of the hydrogen molecule.
Thus, Zinc contains the same mole as a hydrogen molecule. Therefore, zinc contains $0.126mol$
It is known that mole can be obtained by dividing the mass of the solution by its molecular weight.
Thus, $0.126 = \dfrac{{weight}}{{65.38g/mol}}$
$weight = 0.126mol \times 65.38g/mol$
$weight = 8.23g$
Thus, $8.23g$ of zinc will have to be reacted with an excess of dilute HCl solution to produce sufficient hydrogen gas for completely reacting with the oxygen obtained by decomposing $5.104g$ of potassium chlorate.
Among the four options, option-D has an approximate gram value of zinc reacted with an excess of dilute HCl solution to produce sufficient hydrogen gas for completely reacting with the oxygen obtained by decomposing $5.104g$ of potassium chlorate.

So, the correct answer is Option D.

Note: The important terms used to measure the concentration of a solution are Molarity, Molality, and Normality. Molarity of a solution is defined as the moles of solute per liter of the solution. The molality of a solution is defined as the number of moles of solute present in 1 kg of solvent. The normality of a solution is defined as the weight of the solute per litre of the solution.