Mole Concept and Some Basic Concepts of ChemistryhardMCQ SINGLE

Exactly of pure Potassium carbonate () was chemically treated by a complex series of sequential reagMole Concept and Some Basic Concepts of Chemistry Chemistry Question

Question

Exactly $27.6\text{ g}$ of pure Potassium carbonate ($K_2CO_3$) was chemically treated by a complex series of sequential reagents so as to convert absolutely all of its carbon atoms into the coordination complex Potassium zinc hexacyanoferrate(II), $K_2Zn_3[Fe(CN)_6]_2$. Calculate the exact mass of the final product formed.

Answer: A

💡 Solution & Explanation

Step 1: Apply the Principle of Atom Conservation (POAC) on Carbon. Moles of $K_2CO_3$ = $27.6\text{ g} / 138\text{ g/mol} = 0.2\text{ moles}$. Since each $K_2CO_3$ has 1 Carbon, moles of C atoms = $0.2\text{ moles}$. Step 2: The product $K_2Zn_3[Fe(CN)_6]_2$ contains exactly 12 Carbon atoms per molecule. Therefore, Moles of product = $\frac{\text{Moles of C}}{12} = \frac{0.2}{12} = 0.01667\text{ moles}$. Step 3: Calculate Molar mass of product = $(39\times 2) + (65.4\times 3) + (56\times 2) + (12\times 12) + (14\times 12) = 78 + 196.2 + 112 + 144 + 168 = 698.2\text{ g/mol}$. Step 4: Mass = $0.01667 \times 698.2 = 11.6\text{ g}$.

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