Calculate the final temperature of the solution

In summary, the conversation is about the dissolution of CaCl2 and calculating the final temperature of the solution after a 10.6-g sample of CaCl2 is dissolved in 109 g of water. The solution has a specific heat capacity of 4.18 J/°C · g and no heat is lost to the surroundings. The correct answer is obtained by using the equation Q=mcΔT and finding the amount of CaCl2 needed to produce 81.5 kJ of heat.
  • #1
JessicaHelena
188
3

Homework Statement


Consider the dissolution of CaCl2.
CaCl2(s)
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Ca2+(aq) + 2 Cl-(aq) ΔH = -81.5 kJ
A 10.6-g sample of CaCl2 is dissolved in 109 g of water, with both substances at 25.0°C. Calculate the final temperature of the solution assuming no heat lost to the surroundings and assuming the solution has a specific heat capacity of 4.18 J/°C · g.

Homework Equations


Q=mcΔT

The Attempt at a Solution


I had thought Q=ΔH = -81.5kJ = -81.5 x 10^3 J
the mass would be 10.6+109 g
and since the solution overall has a heat capacity of 4.18 J/°Cg, I plugged the numbers in:
81.5 x 10^3 = (10.6+109)x4.18x(T_f-25)
Then I got T_f = 188 °C, which is wrong, but I don't understand why. I don't have much time until the assignment is due, so could someone please help me out? Thank you!
 

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  • #2
How much CaCl2 do you need to get 81.5 kJ?
 
  • #3
@mjc123 I believe 1 mole...?
 
  • #4
And how many moles of CaCl2 have you got?
 
  • #5
@mjc123 Oh I get it now. 10.6g/M(CaCl2), multiply that by 81.5, and that's the Q value.
 
  • #6
@mjc123 Thank you — I got a correct answer! Could please you help me with another problem I posted, though?
 

FAQ: Calculate the final temperature of the solution

1. How do you calculate the final temperature of a solution?

The final temperature of a solution can be calculated by using the formula Q = mCΔT, where Q represents the heat absorbed or released by the solution, m is the mass of the solution, C is the specific heat capacity of the solution, and ΔT is the change in temperature. By plugging in the known values and solving for ΔT, you can determine the final temperature of the solution.

2. What factors can affect the final temperature of a solution?

The final temperature of a solution can be affected by a variety of factors, including the initial temperature of the solution, the amount of heat added or removed, the specific heat capacity of the solution, and the mass of the solution. Other factors such as environmental conditions, the type of container used, and any chemical reactions taking place within the solution can also impact the final temperature.

3. How does the specific heat capacity of a solution affect the final temperature?

The specific heat capacity of a solution is the amount of heat required to raise the temperature of 1 gram of the solution by 1 degree Celsius. The higher the specific heat capacity, the more heat is required to raise the temperature of the solution. This means that a solution with a higher specific heat capacity will have a lower final temperature compared to a solution with a lower specific heat capacity when the same amount of heat is added or removed.

4. Can the final temperature of a solution be negative?

Yes, the final temperature of a solution can be negative if the heat removed from the solution is greater than the heat added. This can occur if the initial temperature of the solution is already below the ambient temperature, or if the heat removed is due to a chemical reaction or phase change within the solution.

5. How can the final temperature of a solution be used in real-life applications?

The final temperature of a solution is an important factor in various real-life applications, such as in cooking, chemical reactions, and industrial processes. By accurately calculating the final temperature, scientists and engineers can determine the efficiency and effectiveness of these processes and make adjustments to improve them. The final temperature can also be used to predict the outcome of a chemical reaction or to ensure that a solution is safe to handle or consume.

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