A calorimeter contains 32.0 of water at 11.5. When 1.70 of (a substance with a molar mass of 74.0 ) is added, it dissolves via the reaction
and the temperature of the solution increases to 26.5.
Calculate the enthalpy change, , for this reaction per mole of .
Assume that the specific heat and density of the resulting solution are equal to those of water [4.18 and 1.00 ] and that no heat is lost to the calorimeter itself, nor to the surroundings.
No units listed.
To calculate the enthalpy change for this reaction per mole of the substance, we need to use the equation:
ΔH = q / n
where ΔH is the enthalpy change, q is the heat absorbed or released during the reaction, and n is the number of moles of the substance involved in the reaction.
First, we need to calculate the heat absorbed or released during the reaction (q). We can use the equation:
q = m * c * ΔT
where q is the heat, m is the mass, c is the specific heat capacity, and ΔT is the change in temperature.
In this case, we are assuming the specific heat capacity and density of the resulting solution to be equal to those of water, so c = 4.18 J/g°C. Also, the mass of the solution is the sum of the mass of water and the mass of the substance, so m = (mass of water + mass of substance).
1. Calculate the mass of water:
mass of water = volume of water * density of water
mass of water = 32.0 g * 1.00 g/mL = 32.0 g
2. Calculate the mass of the substance:
mass of substance = number of moles of substance * molar mass of substance
number of moles of substance = mass of substance / molar mass of the substance = 1.70 g / 74.0 g/mol
Now, we can calculate the heat absorbed or released during the reaction (q):
q = (mass of water + mass of substance) * 4.18 J/g°C * (26.5°C - 11.5°C)
Next, we need to calculate the number of moles of the substance involved in the reaction (n):
n = mass of substance / molar mass of the substance
Finally, we can calculate the enthalpy change (ΔH):
ΔH = q / n
These calculations will give you the enthalpy change per mole of the substance involved in the reaction.