JEE Advanced · Chemistry · 1. Mole Concept
Paragraph:
Chemical reactions involve interaction of atoms and molecules. A large number of atoms/molecules (approximately \(6.023 \times 10^{23}\) ) are present in a few grams of any chemical compound varying with their atomic/molecular masses. To handle such large numbers conveniently, the mole concept was introduced. This concept has implications in diverse areas such as analytical chemistry, biochemistry, electrochemistry and radiochemistry. The following example illustrates a typical case, involving chemical/electrochemical reaction, which requires a clear understanding of the mole concept.
A \(4.0\) molar aqueous solution of \(\mathrm{NaCl}\) is prepared and \(500 \mathrm{~mL}\) of this solution is electrolysed. This leads to the evolution of chlorine gas at one of electrodes (atomic mass: \(\mathrm{Na}=23, \mathrm{Hg}=200 ; 1\) faraday \(=96500\) coulombs).
Question:
The total number of moles of chlorine gas evolved is
- A \(0.5\)
- B \(1.0\)
- C \(2.0\)
- D \(3.0\)
Answer & Solution
Correct Answer
(B) \(1.0\)
Step-by-step Solution
Detailed explanation
\(4.0 \mathrm{M} \mathrm{NaCl} .500 \mathrm{~mL}(0.5 \mathrm{~L})\)
Moles of \(\mathrm{NaCl}=4 \times 0.5=2\)
2 moles \(\mathrm{NaCl} \equiv 2\) moles \(\mathrm{Cl}^{-}\)
\(\underset{2 \text { mole }}{2 \mathrm{Cl}^{-}} \longrightarrow \mathrm{Cl}_2\)
Moles of \(\mathrm{NaCl}=4 \times 0.5=2\)
2 moles \(\mathrm{NaCl} \equiv 2\) moles \(\mathrm{Cl}^{-}\)
\(\underset{2 \text { mole }}{2 \mathrm{Cl}^{-}} \longrightarrow \mathrm{Cl}_2\)
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