A 100.0 mL sample of 0.300 mol L^-1 NaOH is mixed with a 100.0 mL sample of 0.300 mol L^-1 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 $D _ { \mathrm { r } }$ H° (in units of kJ $\mathrm { mol } ^ { - 1 }$ )for the neutralization reaction between aqueous NaOH and HNO₃ .Assume 1)that no heat is lost to the calorimeter or the surroundings,and 2)that the density and the heat capacity of the resulting solution are the same as water.

Question

Quizplus · Accepted Answer

First, we need to calculate the heat absorbed by the reaction (qrxn). qrxn = -qcal = -Ccal(Tfinal - Tinitial) where Ccal is the heat capacity of the calorimeter and can be calculated using the mass of the water in the calorimeter and its heat capacity. Since the density and heat capacity of the solution are assumed to be the same as water, we can assume that the mass of the water in the calorimeter is 200.0 g (100.0 mL + 100.0 mL) and its heat capacity is 4.184 J/g°C. Therefore, Ccal = (200.0 g)(4.184 J/g°C) = 836.8 J/°C. Next, we need to calculate the amount of heat produced by the reaction. We can do this by calculating the amount of moles of either NaOH or HNO₃ that reacted and using the molar enthalpy of the reaction. Since the two solutions have the same concentration and volume, we can assume that they reacted completely in a 1:1 stoichiometric ratio. Therefore, the amount of moles of either reactant can be calculated as: n = (0.300 mol/L)(0.100 L) = 0.0300 mol Now we can use the molar enthalpy of the reaction to calculate the amount of heat produced: qrxn = nΔH°rxn Since ΔH°rxn is what we're trying to find, we can rearrange the equation to solve for it: ΔH°rxn = qrxn/n Plugging in the values we found earlier: qrxn = -Ccal(Tfinal - Tinitial) = -(836.8 J/°C)(37.00°C - 35.00°C) = -1673.6 J ΔH°rxn = -1673.6 J / 0.0300 mol = -55,787.6 J/mol Converting to kJ/mol gives us an answer of -55.8 kJ/mol, which is closest to choice A. Therefore, the answer is A.

A 1000 ML Sample of 0 DrD _ { \mathrm { r } }Dr​

A 1000 ML Sample of 0 $D _ { \mathrm { r } }$