The reaction of hydrochloric acid and sodium hydroxide is exothermic
HCl +NaOH --> NaCl + H2O
In one experiment, a student placed 50.0 mL of 1.00 M HCl at 25.5 oC in a coffee cup calorimeter. To this was added 50.0 mL of 1.00 M NaOH solution, also at 25.5 oC. The mixture was stirred and the temperature rose to 37.8 oC. What is the heat of reaction in joules per mole of HCl? Assume the specific heat of the solutions is 4.184 J/g oC, densities are 1.00 g/mL, and no heat is lost to the cup or to the air.
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To determine the heat of reaction for this exothermic reaction, we will need to use the equation:
q = m * c * ΔT
Where:
- q is the heat absorbed or released by the reaction (in joules)
- m is the mass of the solution (in grams)
- c is the specific heat capacity of the solution (in J/g oC)
- ΔT is the change in temperature (in oC)
First, let's find the mass of the solution. We have 50.0 mL of HCl and 50.0 mL of NaOH, so the total volume is 100.0 mL or 100.0 grams (since the density is 1.00 g/mL).
Next, we need to calculate the change in temperature. ΔT is the final temperature minus the initial temperature. In this case, the initial temperature is 25.5 oC, and the final temperature is 37.8 oC. So, ΔT = 37.8 oC - 25.5 oC = 12.3 oC.
Now, we can calculate the heat of reaction:
q = m * c * ΔT
q = 100.0 g * 4.184 J/g oC * 12.3 oC
q = 5142.45 J
Finally, to find the heat of reaction per mole of HCl, we need to divide the heat by the number of moles of HCl used. Since the concentration of HCl is 1.00 M and we used 50.0 mL (which is equivalent to 0.0500 L), we can calculate the number of moles:
moles of HCl = concentration * volume
moles of HCl = 1.00 M * 0.0500 L
moles of HCl = 0.0500 mol
Now, divide the heat (in joules) by the number of moles:
heat of reaction per mole of HCl = 5142.45 J / 0.0500 mol
heat of reaction per mole of HCl = 102,849 J/mol
So, the heat of reaction for this exothermic reaction is approximately 102,849 J/mol of HCl.