Question

Chemistry

Posted 5 months ago

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16. For parts of the free response queatlon th. Open with atiows, clearly thow the marthod used and the steps involved in arriving at your answers. You must siow your work to receive credit for your answer.
Examples and equations may be included in your answers where appropriate.
A student wishes to determine the concentration of $\mathrm{Ag}^{+}(a q)$ in a solution of $\mathrm{AgNO}_{3}(a q)$. The student combines $10.00 \mathrm{~mL}$ of $\mathrm{AgNO}_{3}(\mathrm{aq})$ with excess $\mathrm{Na}_{2} \mathrm{SO}_{4}(\mathrm{aq})$ and observes the formation of a white precipitate. The formation of the precipitate is represented by the following equation.
$2 \mathrm{AgNO}_{3}(a q)+\mathrm{Na}_{2} \mathrm{SO}_{4}(a q) \rightarrow \mathrm{Ag}_{2} \mathrm{SO}_{4}(s)+2 \mathrm{NaNO}_{3}(a q)$
(a) Write the balanced net ionic equation for the precipitation reaction.
The student collects the precipitate by filtration and measures the mass of the filter paper and precipitate every 10 minutes as it dries. The student records the data in the following table.
\begin{tabular}{|c|c|}
\hline \multicolumn{1}{|c|}{ Mass of dry filter paper } & $0.88 \mathrm{~g}$ \\
\hline Mass of filter paper and precipitate immediately after filtration & $4.82 \mathrm{~g}$ \\
\hline Mass of filter paper and precipitate after 10 minutes & $4.37 \mathrm{~g}$ \\
\hline Mass of filter paper and precipitate after 20 minutes & $4.01 \mathrm{~g}$ \\
\hline Mass of filter paper and precipitate after 30 minutes & $3.79 \mathrm{~g}$ \\
\hline
\end{tabular}
(b) Use the data above to calculate the number of moles of $\mathrm{Ag}_{2} \mathrm{SO}_{4}(s)$ (molar mass $311.8 \mathrm{~g} / \mathrm{mol}$ ) that precipitated.
(c) Calculate the concentration of $\mathrm{Ag}^{\dagger}(a q)$ in the original $10.00 \mathrm{~mL}$ solution of $\mathrm{AgNO}_{3}(a q)$.
(d) The concentration of $\mathrm{Ag}^{+}(a q)$ determined by the student is significantly higher than the actual concentration of $\mathrm{Ag}^{+}(\mathrm{aq})$ Based on the student's data table, identify an error in the experimental procedure that led to this result:
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Answer from Sia

Posted 5 months ago

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1 Answer

\mathrm{Ag}^+_{(aq)} + \mathrm{SO}_4^{2-}_{(aq)} \rightarrow \mathrm{Ag}_2\mathrm{SO}_4_{(s)}

2 Answer

Number of moles of $\mathrm{Ag}_2\mathrm{SO}_4$ = $\frac{(3.79 \mathrm{~g} - 0.88 \mathrm{~g})}{311.8 \mathrm{~g/mol}}$

3 Answer

Concentration of $\mathrm{Ag}^+$ = $\frac{\text{moles of } \mathrm{Ag}_2\mathrm{SO}_4 \times 2}{0.01000 \mathrm{~L}}$

4 Answer

Possible error: Incomplete drying of the precipitate, leading to an overestimation of the mass of $\mathrm{Ag}_2\mathrm{SO}_4$.

Key Concept

The net ionic equation represents the ions that participate directly in the reaction, forming the precipitate.

Explanation

The net ionic equation excludes spectator ions and shows the formation of the insoluble compound.

Key Concept

The number of moles of a compound is calculated by dividing its mass by its molar mass.

Explanation

This calculation is essential for stoichiometry, allowing us to relate mass to moles for chemical reactions.

Key Concept

The concentration of ions in a solution is determined by the number of moles of the ion divided by the volume of the solution.

Explanation

This relationship is used to find the molarity of a solution, which is a measure of its concentration.

Key Concept

Experimental errors can affect the accuracy of the results.

Explanation

Identifying potential errors helps in understanding discrepancies between expected and observed results.

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