A 150.0 mL sample of a 1.50 M solution of CuSO4
is mixed with a 150.0 mL sample of 3.00 M
KOH in a coffee cup calorimeter. The temperature of both solutions and the calorimeter was
25.2°C before mixing and 31.3°C after mixing. The heat capacity of the calorimeter is 24.2 J/K.
Calculate the ΔHrxn for this reaction in units of kJ / mol of copper (II) hydroxide.
Assume the solutions is dilute enough that the specific heat and density of the solution is the same as that
of water.
mols CuSO4 = M x L = 1.50 x 0.150 = 0.225
mols KOH = 3.00 x 0.150 = 0.450
specific heat solns = specific heat H2O = 4.18 J/K*C
CuSO4 + 2KOH = Cu(OH)2 + 2H2O
q = mass solutions x specific heat solns x (Tfinal-Tinitial) + Ccal*deltat T
q = 300g x 4.18 x (31.3-25.2) + 24.2*(31.3-25.2)
dHrxn in J/mol= q/0.225 mol CuSO4
Then convert to kJ/mol
34 J
thank you dr bob XDXD
To find the ΔHrxn (enthalpy change for the reaction), we can use the equation:
ΔHrxn = q / n
Where:
- ΔHrxn is the enthalpy change for the reaction
- q is the heat released or absorbed by the reaction
- n is the number of moles of the reactant or product involved in the reaction
First, calculate the heat released or absorbed (q) by the reaction using the equation:
q = m * c * ΔT
Where:
- q is the heat released or absorbed by the reaction,
- m is the mass of the solution. Since the volume and density of the solution are not given, we can assume the density of the solution is equal to that of water (1 g/mL). So, m = volume * density
- c is the specific heat capacity of the solution, which is the same as water (4.18 J/g°C)
- ΔT is the change in temperature (Tf - Ti)
Next, calculate the moles of copper (II) hydroxide (Cu(OH)2) involved in the reaction.
CuSO4 + 2 KOH → Cu(OH)2 + K2SO4
From the balanced equation, we can see that 1 mole of CuSO4 reacts to form 1 mole of Cu(OH)2. So, the number of moles of Cu(OH)2 is equal to the number of moles of CuSO4.
Now, let's calculate the values.
1. Calculate the mass of the solution:
Since the density of water is 1 g/mL, the mass of the solution is equal to its volume in mL.
Volume of the solution = 150.0 mL + 150.0 mL = 300.0 mL
Mass of the solution = Volume of the solution * Density of water
2. Calculate the change in temperature (ΔT):
ΔT = Tf - Ti = (31.3°C - 25.2°C)
3. Calculate the heat released or absorbed (q):
q = m * c * ΔT
4. Calculate the number of moles of Cu(OH)2:
Since the reaction is 1:1 between CuSO4 and Cu(OH)2, the number of moles of Cu(OH)2 is the same as the number of moles of CuSO4.
5. Calculate ΔHrxn:
ΔHrxn = q / n
To convert ΔHrxn to kJ/mol, divide the ΔHrxn by 1000.
Finally, the ΔHrxn for this reaction, in units of kJ/mol of copper (II) hydroxide, is the calculated value.