when 5.0g of KOH is added to 100mL, of water, the temperature of the solution increases by 3 degrees celsius. Assume the density of the solution to be 1g/mL and specific heat capacity of the solution to be 4.184 J/g K.
a. calculate the amount of heat absorbed by the solution.
b. find the enthalpy change for the dissolution of KOH.
c. find the enthalpy change per mole KOH.
1.
q = mass H2O x specific heat H2O x (Tfinal-Tinitial)
2.
q/gram = q/5.0
q/mol = (q/5.0)*molar mass KOH
Divide by 1000 to express in kJ/mol which is the usual unit used.
To answer these questions, we can use the following equation for calculating the amount of heat absorbed or released:
q = mcΔT
Where:
q = amount of heat (in joules)
m = mass (in grams)
c = specific heat capacity (in J/g K)
ΔT = change in temperature (in degrees Celsius or Kelvin)
Now, let's calculate each part of the question step by step:
a. To calculate the amount of heat absorbed by the solution, we need to determine the mass of the solution. We have 5.0g of KOH dissolved in 100mL of water. Since the density of the solution is 1g/mL, this means that the mass of the solution is also 100g.
Substituting the values into the equation:
q = (100g) × (4.184 J/g K) × (3°C)
b. To find the enthalpy change for the dissolution of KOH, we can consider that the heat absorbed by the solution is equal to the enthalpy change (∆H) of the process. Therefore, the value of q calculated in part a represents the enthalpy change.
c. Lastly, to find the enthalpy change per mole of KOH, we need to know the molar mass of KOH. The molar mass of KOH is approximately 56.11 g/mol.
Substituting the values into the equation:
∆H (per mole KOH) = (∆H) / (moles of KOH)
moles of KOH = (5.0g) / (56.11 g/mol)
Once we have the moles of KOH, we can calculate the enthalpy change per mole KOH using the value of ∆H from part b.
It is important to note that the enthalpy change is negative for an exothermic process (heat is released) and positive for an endothermic process (heat is absorbed). By using the equation q = mcΔT, you can calculate the heat exchange in various situations involving temperature changes and specific heat capacities.