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Multiple Choice
A 100.0 mL sample of 0.300 M NaOH is mixed with a 100.0 mL sample of 0.300 M HNO3 in a coffee cup calorimeter. If both solutions were initially at 35.00°C and the temperature of the resulting solution was recorded as 37.00°C, determine the ΔH°rxn (in kJ/mol) for the neutralization reaction.
A
-25.0 kJ/mol
B
-57.3 kJ/mol
C
25.0 kJ/mol
D
57.3 kJ/mol
Verified step by step guidance
1
Start by identifying the chemical reaction taking place. The neutralization reaction between NaOH and HNO3 can be represented as: .
Calculate the number of moles of NaOH and HNO3. Since both solutions have the same concentration and volume, the number of moles for each is: , where and (convert mL to L).
Determine the heat absorbed or released by the solution using the formula: , where is the mass of the solution, is the specific heat capacity (assume water's specific heat capacity, ), and is the change in temperature.
Convert the heat absorbed or released from joules to kilojoules, and then calculate the enthalpy change per mole of reaction. Use the formula: , where is the number of moles of the limiting reactant.
Consider the sign of . Since the temperature increased, the reaction is exothermic, and should be negative.