42. Exactly 500 mL of a 4.0 M aqueous solution is electrolysed entirely using a liquid Mercury () ca — Electrochemistry Chemistry Question
Question
42. Exactly 500 mL of a 4.0 M aqueous $NaCl$ solution is electrolysed entirely using a liquid Mercury ($Hg$) cathode. What is the maximum theoretical mass of sodium amalgam ($NaHg$) formed? (Atomic mass: Na=23, Hg=200)
Answer: B
💡 Solution & Explanation
500 mL of 4.0 M $NaCl$ contains 2.0 moles of $Na^+$. On a mercury cathode, the high overvoltage of $H_2$ allows $Na^+$ to discharge, forming the amalgam $NaHg$. 2.0 moles of $Na^+$ form 2.0 moles of $NaHg$. Total Mass = $2.0 \times (23 + 200) = 446$ g.
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