An excess of aluminum metal is added to 200.0 mL of 0.025 M solution of CuCl2, reducing the Cu+2 ions to metallic Cu. If the temperature of the solution increases from 25.0 to 27.5 degrees celsius, what is the enthalpy of this reaction per mole of Cu formed? (Specific heat of solution = 4.18 J/gK)
a) 2.09 kJ
B) 23.0 kJ
C) 83.6 kJ
D) 418 kJ
I wrote out the equation:
3 CuCl2 + 2Al = 2AlCl3 + 3Cu
There are 0.005 moles of CuCl2 present, so that will result in 0.005 moles of Cu. I found the mass and plugged it into the q=mc(change in T) equation, but got an answer different from those above. Help? Thansk!
your heat: 200*4.18*2.5 J
heat per mole=your heat/(.005)
= about 2000/.005J=about 400kJ
work it accurately and see if D is correct.
23.5
To calculate the enthalpy of the reaction per mole of Cu formed, you need to use the equation q = mcΔT, where q is the heat absorbed or released in the reaction, m is the mass, c is the specific heat capacity of the solution, and ΔT is the change in temperature.
To solve the problem, follow these steps:
Step 1: Determine the heat absorbed or released in the reaction.
Since aluminum reacts with copper(II) chloride to form aluminum chloride and metallic copper, we know that the reaction is exothermic, which means heat is released.
Step 2: Calculate the mass of the solution.
To do this, convert the volume of the solution to grams using the density of the solution, which should be given in the question or in supplementary information. Then, multiply the density by the volume to get the mass of the solution.
Step 3: Calculate the mass of Cu.
You correctly determined that there are 0.005 moles of Cu formed. To find the mass of Cu formed, multiply the number of moles by the molar mass of Cu.
Step 4: Calculate the heat absorbed or released.
Using the equation q = mcΔT, plug in the values you have:
q = (mass of solution + mass of Cu) × specific heat capacity of the solution × ΔT
Step 5: Convert the answer to kilojoules (kJ).
Since the answer choices are given in kJ, convert the calculated answer from joules to kilojoules by dividing by 1000.
Now, let's go through the calculations using the given information.
Given:
Volume of solution (V) = 200.0 mL = 200.0 g (assuming the density is 1 g/mL)
Concentration of CuCl2 (C) = 0.025 M
Temperature change (ΔT) = 27.5 °C - 25.0 °C = 2.5 °C
Specific heat capacity (c) = 4.18 J/gK
Step 1:
Since the reaction is exothermic, heat is released during the process.
Step 2:
mass of solution = V = 200.0 g
Step 3:
Number of moles of Cu formed = 0.025 M × 0.200 L = 0.005 moles
molar mass of Cu = 63.55 g/mol
mass of Cu formed = 0.005 moles × 63.55 g/mol = 0.318 g
Step 4:
q = (mass of solution + mass of Cu) × c × ΔT
= (200.0 g + 0.318 g) × 4.18 J/gK × 2.5 K
= 839.16 J
Step 5:
q = 839.16 J = 0.83916 kJ
So, the enthalpy of the reaction per mole of Cu formed is approximately 0.83916 kJ.
Therefore, none of the given answer choices match the calculated value. Double-check your calculations and solve the problem again to get the correct answer.