27. 0 mL of 1.00 M HClO4 are mixed with 27.0 mL of 1.00 M LiOH in a coffee cup calorimeter. The calorimeter constant is 28.1 J/Celsius. Both were initialized at 23.31 degrees Celsius. Calculate change Hrxn (in kJ/mol) for the reaction.
What's the final temperature?
It just says, both solutions were initially 21.31 degrees Celsius, not 23.3 1 and specific heat was 4.18 J/g degrees Celsius.
Final temp was 27.35 degrees celsius
HClO4 + LiOH ==> H2O + LiClO4
mols LiOH = M x L = 0.027
mols HClO4 = M x L = 0.027
q = [mass H2O x specific heat H2O x (Tfinal-Tinitial)] + [(Ccal*(Tfinal-Tinitial)] where Ccal = heat capacity of calorimeter.
mass H2O = 54 mL solution = 54 grams.
dH/mol = q/0.027 and change to kJ/mol.
Thank You!!!
To calculate the change in enthalpy of the reaction (ΔHrxn) in kJ/mol, we need to use the equation:
ΔHrxn = qrxn / n
Where:
- ΔHrxn is the change in enthalpy of the reaction in kJ/mol
- qrxn is the heat absorbed or released by the reaction, in joules
- n is the number of moles of the limiting reactant
First, we need to find the number of moles for each reactant. We can use the equation:
moles = concentration * volume
For HClO4:
moles of HClO4 = (1.00 M) * (0.0270 L) = 0.0270 mol
For LiOH:
moles of LiOH = (1.00 M) * (0.0270 L) = 0.0270 mol
Since both reactants have the same number of moles, we can conclude that LiOH is the limiting reactant.
Next, we need to calculate the heat absorbed or released by the reaction (qrxn). We can use the equation:
qrxn = -Ccal * ΔT
Where:
- qrxn is the heat absorbed or released by the reaction, in joules
- Ccal is the calorimeter constant, given as 28.1 J/°C
- ΔT is the change in temperature of the reaction
The change in temperature (ΔT) can be found by subtracting the initial temperature from the final temperature. In this case, both were initialized at 23.31°C.
Let's say the final temperature is Tfinal.
ΔT = Tfinal - Tinitial
ΔT = Tfinal - 23.31°C
Now, we have all the necessary information to calculate ΔHrxn.
ΔHrxn = qrxn / n
ΔHrxn (in kJ/mol) = (qrxn / 1000) / n
Since the units of Ccal are J/°C and we need the temperature difference in Celsius, we don't need to convert the temperatures to Kelvin.
To calculate qrxn, we need the change in temperature (ΔT). However, the question doesn't provide the final temperature, so we cannot proceed further without that information.
Please provide the final temperature so that we can continue with the calculation.