Concept explainers
A student performing a calorimetry experiment combined 100.0 ml. of 0.50 M HCI and 100.0 ml. of 0.50 M NaOH in a StyrofoamTM cup calorimeter. Both solutions were initially at 20.0
(a) Suppose the experiment is repeated in the same calorimeter but this time using 200 mL of 0.50 M HCl and 200.0 ml of 0.50 M NaOH. WIII the AT observed be greater than, less than, or equal to that in the first experiment, and why?
(b) Suppose that the experiment is repeated once again in the same calorimeter, this time using 100 mL of 1.00 M HCI and 100.0 ml. of 1.00 M NaOH. Will the
a.
Interpretation:
Changes in temperature in a different experiment performed in the same calorimeter but with two different solutions should be compared to the change in temperature observed in another experiment which was performed before.
Concept Introduction:
Heat released during a chemical reaction in a calorimeter is calculated by applying the formula:
Here, m = mass of the solution
Cp = specific heat of the reacting solution
ΔT= change in temperature
In a Styrofoam calorimeter, the pressure is constant. Heat released at a constant pressure is known as the enthalpy of the chemical reaction.
In the first experiment, the chemical equation is:
Total volume of the reacting solution = 100 mL + 100 mL = 200 mL
Mass of the reacting solution
[The solution is aqueous and density of water is 1 g/mL].
Therefore,
At constant pressure, enthalpy of the system = 2677.76 J.
Answer to Problem 9.79PAE
Solution:
The observed
value will be less than the first experiment because of the value of
depends on the values of mass and specific heat of the solution. The mass of the reacting solution is more in this experiment.
Explanation of Solution
In this experiment, total volume of the reacting solution = (200 + 200) mL = 400 mL
Mass of the reacting solution
[The solution is aqueous and density of water is 1 g/mL].
We know, = 2677.76 J
Therefore at constant pressure,
The value of
in the first experiment equals to
Therefore, the observed
value will be less than the first experiment.
b.
Interpretation:
Changes in temperature in a different experiment performed in the same calorimeter but with two different solutions should be compared to the change in temperature observed in another experiment which was performed before.
Concept Introduction:
Heat released during a chemical reaction in a calorimeter is calculated by applying the formula:
Here, m = mass of the solution
Cp = specific heat of the reacting solution
ΔT = change in temperature
In a Styrofoam calorimeter, the pressure is constant. Heat released at a constant pressure is known as the enthalpy of the chemical reaction.
In the first experiment, the chemical equation is:
Total volume of the reacting solution = 100 mL + 100 mL = 200 mL
Mass of the reacting solution
[The solution is aqueous and density of water is 1 g/mL].
Therefore,
At constant pressure, enthalpy of the system = 2677.76 J.
Answer to Problem 9.79PAE
Solution:
The observed
value will be equal to that in the first experiment because of the value of
depends on the values of mass and specific heat of the solution. The mass of the reacting solution is same as that in the first experiment.
Explanation of Solution
In this experiment, total volume of the reacting solution = (100 + 100) mL = 200 mL
Mass of the reacting solution
[The solution is aqueous and density of water is 1 g/mL].
We know, = 2677.76 J
Therefore at constant pressure,
The value of ΔT in the first experiment equals to 3.20C
Therefore, the observed ΔT value will be equal to that in the first experiment.
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Chapter 9 Solutions
Chemistry for Engineering Students
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