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Sia

青州's Question
Chemistry
Posted 4 months ago

In a coffee cup calorimeter, 14.0 mL14.0 \mathrm{~mL} of 0.65M0.65 \mathrm{M} nitric acid (HNO3)\left(\mathrm{HNO}_{3}\right) and 14.0 mL14.0 \mathrm{~mL} of 0.65M0.65 \mathrm{M} potassium hydroxide (KOH)(\mathrm{KOH}) are mixed to observe the heat released during the neutralization reaction. Based on the data in the table, what is the enthalpy of the neutralization reaction between HNO3\mathrm{HNO}_{3} and KOH\mathrm{KOH} ?
\begin{tabular}{|c|c|}
\hline Initial temperature in the calorimeter (C)\left({ }^{\circ} \mathrm{C}\right) & 21.9 \\
\hline Final temperature in the calorimeter (C)\left({ }^{\circ} \mathrm{C}\right) & 26.2 \\
\hline Final mass of the neutralized solution (g)(\mathrm{g}) & 27.91 \\
\hline Calorimeter constant (J/C))\left.\left(\mathrm{J} /{ }^{\circ} \mathrm{C}\right)\right) & 4.47 \\
\hline
\end{tabular}
ΔHrxn=kJ/mol
\Delta H_{\mathrm{rxn}}=\square \mathrm{kJ} / \mathrm{mol}

\square
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Answer from Sia
Posted 4 months ago
Solution
1
Identify the reaction: The reaction between nitric acid (HNO3\mathrm{HNO}_{3}) and potassium hydroxide (KOH\mathrm{KOH}) is a neutralization reaction, which can be represented as: HNO3+KOHKNO3+H2O\mathrm{HNO}_{3} + \mathrm{KOH} \rightarrow \mathrm{KNO}_{3} + \mathrm{H}_{2}\mathrm{O}
2
Calculate the heat absorbed by the solution: The heat absorbed by the solution (qsolutionq_{\text{solution}}) can be calculated using the formula: qsolution=mcΔTq_{\text{solution}} = m \cdot c \cdot \Delta T where mm is the mass of the solution, cc is the specific heat capacity of water (4.18 J/g°C), and ΔT\Delta T is the change in temperature. Given: - m=27.91gm = 27.91 \, \text{g} - ΔT=26.221.9=4.3°C\Delta T = 26.2 - 21.9 = 4.3 \, \text{°C} qsolution=27.91g4.18J/g°C4.3°C=501.6Jq_{\text{solution}} = 27.91 \, \text{g} \cdot 4.18 \, \text{J/g°C} \cdot 4.3 \, \text{°C} = 501.6 \, \text{J}
3
Calculate the heat absorbed by the calorimeter: The heat absorbed by the calorimeter (qcalorimeterq_{\text{calorimeter}}) can be calculated using the formula: qcalorimeter=CcalΔTq_{\text{calorimeter}} = C_{\text{cal}} \cdot \Delta T where CcalC_{\text{cal}} is the calorimeter constant. Given: - Ccal=4.47J/°CC_{\text{cal}} = 4.47 \, \text{J/°C} - ΔT=4.3°C\Delta T = 4.3 \, \text{°C} qcalorimeter=4.47J/°C4.3°C=19.2Jq_{\text{calorimeter}} = 4.47 \, \text{J/°C} \cdot 4.3 \, \text{°C} = 19.2 \, \text{J}
4
Calculate the total heat released: The total heat released (qtotalq_{\text{total}}) is the sum of the heat absorbed by the solution and the calorimeter. qtotal=qsolution+qcalorimeter=501.6J+19.2J=520.8Jq_{\text{total}} = q_{\text{solution}} + q_{\text{calorimeter}} = 501.6 \, \text{J} + 19.2 \, \text{J} = 520.8 \, \text{J}
5
Calculate the moles of reactants: The moles of HNO3\mathrm{HNO}_{3} and KOH\mathrm{KOH} can be calculated using the molarity and volume. Given: - Volume of HNO3\mathrm{HNO}_{3} and KOH\mathrm{KOH} = 14.0 mL each - Molarity of HNO3\mathrm{HNO}_{3} and KOH\mathrm{KOH} = 0.65 M Moles of HNO3=Moles of KOH=0.65M×0.014L=0.0091mol\text{Moles of } \mathrm{HNO}_{3} = \text{Moles of } \mathrm{KOH} = 0.65 \, \text{M} \times 0.014 \, \text{L} = 0.0091 \, \text{mol}
6
Calculate the enthalpy change per mole: The enthalpy change of the reaction (ΔHrxn\Delta H_{\text{rxn}}) can be calculated using the formula: ΔHrxn=qtotalmoles of reactants\Delta H_{\text{rxn}} = \frac{q_{\text{total}}}{\text{moles of reactants}} Given: - qtotal=520.8J=0.5208kJq_{\text{total}} = 520.8 \, \text{J} = 0.5208 \, \text{kJ} - Moles of reactants = 0.0091 mol ΔHrxn=0.5208kJ0.0091mol=57.2kJ/mol\Delta H_{\text{rxn}} = \frac{0.5208 \, \text{kJ}}{0.0091 \, \text{mol}} = 57.2 \, \text{kJ/mol}
Answer
The enthalpy of the neutralization reaction between HNO3\mathrm{HNO}_{3} and KOH\mathrm{KOH} is 57.2kJ/mol57.2 \, \text{kJ/mol}.
Key Concept
Enthalpy change of a reaction can be determined using calorimetry data and the formula ΔHrxn=qtotalmoles of reactants\Delta H_{\text{rxn}} = \frac{q_{\text{total}}}{\text{moles of reactants}}.
Explanation
By calculating the heat absorbed by the solution and the calorimeter, and then dividing by the moles of reactants, we can determine the enthalpy change of the reaction.

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