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Questions and Answers
What does the symbol ΔH represent in thermodynamics?
What does the symbol ΔH represent in thermodynamics?
What is the correct formula to calculate heat absorbed or released by the surroundings?
What is the correct formula to calculate heat absorbed or released by the surroundings?
What does specific heat capacity measure?
What does specific heat capacity measure?
What is the primary purpose of a calorimeter?
What is the primary purpose of a calorimeter?
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In a calorimeter, what is typically the initial temperature of the water when determining heat transfer?
In a calorimeter, what is typically the initial temperature of the water when determining heat transfer?
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Which type of calorimeter maintains constant pressure during the measurement process?
Which type of calorimeter maintains constant pressure during the measurement process?
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What is the significance of measuring the final temperature in a calorimeter?
What is the significance of measuring the final temperature in a calorimeter?
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What does a negative value for ΔH indicate about a reaction?
What does a negative value for ΔH indicate about a reaction?
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If 0.45 grams of copper at 87 degrees Celsius is placed in water at 23 degrees Celsius and reaches 24 degrees Celsius, what component of the calorimeter is important in assessing heat transfer?
If 0.45 grams of copper at 87 degrees Celsius is placed in water at 23 degrees Celsius and reaches 24 degrees Celsius, what component of the calorimeter is important in assessing heat transfer?
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What does the variable ΔT represent in the heat calculation formula?
What does the variable ΔT represent in the heat calculation formula?
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In a Constant Pressure Calorimeter, if the heat is lost by the chemicals, what must happen to the heat in the solution?
In a Constant Pressure Calorimeter, if the heat is lost by the chemicals, what must happen to the heat in the solution?
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Which of the following statements is true about q and ΔH during a reaction at constant pressure?
Which of the following statements is true about q and ΔH during a reaction at constant pressure?
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What does calorimetry primarily focus on?
What does calorimetry primarily focus on?
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What happens to ΔH in an endothermic reaction?
What happens to ΔH in an endothermic reaction?
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Which statement about calorimetry is true?
Which statement about calorimetry is true?
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Which is a common example of a Constant Pressure Calorimeter?
Which is a common example of a Constant Pressure Calorimeter?
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What is the specific heat capacity of titanium determined from the given calculations?
What is the specific heat capacity of titanium determined from the given calculations?
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How much energy did the water gain during the process?
How much energy did the water gain during the process?
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What is the formula used to calculate the heat transfer in water in this experiment?
What is the formula used to calculate the heat transfer in water in this experiment?
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If the mass of water is 100g and its specific heat is 4.184 J/g degrees Celsius, how much heat change occurs from 32 degrees Celsius to 16 degrees Celsius?
If the mass of water is 100g and its specific heat is 4.184 J/g degrees Celsius, how much heat change occurs from 32 degrees Celsius to 16 degrees Celsius?
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What conclusion can be drawn from the exothermic reactions described in the heat of reaction sections?
What conclusion can be drawn from the exothermic reactions described in the heat of reaction sections?
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In the example of heat of reaction using NaOH and HCl, what was the highest temperature reached?
In the example of heat of reaction using NaOH and HCl, what was the highest temperature reached?
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What is the total mass of the ice used in the calorimetry example?
What is the total mass of the ice used in the calorimetry example?
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Using the calorimetry formula, what is the calculated value of the calorimeter's specific heat if Cs is determined as -16.28 J/g degrees Celsius?
Using the calorimetry formula, what is the calculated value of the calorimeter's specific heat if Cs is determined as -16.28 J/g degrees Celsius?
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In the calculation of heat of reaction 2, what is the initial temperature of HCl?
In the calculation of heat of reaction 2, what is the initial temperature of HCl?
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What is ΔH when 20 g of water with a specific heat of 4.184 J/g degrees Celsius is cooled from 38 degrees Celsius to 45 degrees Celsius?
What is ΔH when 20 g of water with a specific heat of 4.184 J/g degrees Celsius is cooled from 38 degrees Celsius to 45 degrees Celsius?
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What is the calculated heat lost by the copper when its temperature decreases from 87 degrees Celsius to 24 degrees Celsius?
What is the calculated heat lost by the copper when its temperature decreases from 87 degrees Celsius to 24 degrees Celsius?
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If water gains 10.91 J of heat energy, what is the corresponding heat lost by the copper in the calorimeter?
If water gains 10.91 J of heat energy, what is the corresponding heat lost by the copper in the calorimeter?
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What is the specific heat capacity of water used in calculations?
What is the specific heat capacity of water used in calculations?
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What was the mass of water calculated in the calorimetry experiment after solving the equation qwater = m x C x ΔT?
What was the mass of water calculated in the calorimetry experiment after solving the equation qwater = m x C x ΔT?
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In the calorimetry example involving titanium, what is the specific heat of titanium if the final temperature was reached in the calorimeter?
In the calorimetry example involving titanium, what is the specific heat of titanium if the final temperature was reached in the calorimeter?
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What is the initial temperature of the water when the calorimetry experiment starts?
What is the initial temperature of the water when the calorimetry experiment starts?
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What is the change in temperature (ΔT) for the water during the experiment given its initial and final temperatures?
What is the change in temperature (ΔT) for the water during the experiment given its initial and final temperatures?
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In the formula for heat transfer, what does the variable 'm' represent?
In the formula for heat transfer, what does the variable 'm' represent?
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Study Notes
Prayer Before Class
- Holy Spirit, true source of wisdom and light, dissipate darkness and ignorance
- Grant a penetrating mind, good memory, and ease of learning
- Guide the work and bring it to successful completion through Jesus Christ
- A prayer for focus and success in classwork
Post-laboratory Discussion Experiment 5: Calorimetry
- Unit Intended Learning Outcome: Students should be able to determine the heat absorbed or released when a solid dissolves in water to form a solution and compare the heat involved in three related reactions.
- Calorimetry: Science to determine changes in energy in a system by measuring heat released or absorbed during a chemical reaction
-
Calorimeter: Apparatus to measure quantity and direction of heat flow during a physical change
- Measuring ΔH
- Used to understand ΔH (change in enthalpy or heat of reaction):
- Negative for exothermic reactions
- Positive for endothermic reactions
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Two Main Types of Calorimeters:
- Bomb Calorimeter: Maintains constant volume during process
- Constant Pressure Calorimeter: Maintains constant pressure, volume changes may occur (e.g., coffee cup calorimeter)
Constant Pressure Calorimeter
- Uses the first law of thermodynamics: Heat lost = heat gained
- The heat absorbed or released by a reaction at constant pressure is the same as the change in enthalpy (ΔH)
- Heat and enthalpy change are interchangeable: q = ΔH
- ΔH can be determined by measuring the heat flow at constant pressure
Constant Pressure Calorimeter – Specific Heat Capacity
- Amount of energy (heat) expressed in joules (J) to raise the temperature of 1 gram of a substance by 1 degree Celsius
Constant Pressure Calorimeter – Procedure
- To measure enthalpy change for a reaction in an aqueous solution:
- Dissolve reacting chemicals (system) in known volumes of water (surroundings) in a foam cup calorimeter
- Measure initial temperature of each solution, mix solutions in the cup
- After reaction, measure the final temperature (the constant temperature) of the mixed solutions
- Use the formula q = m x C x ΔT to calculate heat, given mass (m), specific heat (C), and change in temperature (ΔT)
- The heat absorbed by the surroundings (qsurr) is equal to, but with the opposite sign of, the heat released by the system (qsys):
- qsurr = -qsys
- The enthalpy change for the reaction (ΔH) is calculated as:
- qsys = ΔH = -qsurr = -m x C x ΔT
Calculations:
- Example – Copper A 0.45 gram copper sample (initial temp: 87°C, Ccopper = .385 J/g °C) was placed in water (Initial temperature: 23°C, Cwater = 4.184 J/g °C). Equilibrium at 24°C, What is the mass of water in the calorimeter?: - Solution needs m of water in the calorimeter using the above equation
Additional Topics/Calculations:
- Different examples of the use of calorimeters to determine and calculate specific heat of titanium
- Applying the concept to determining heat capacity/change of Calorimeters
- Determining heat capacity from data/ calculations
- Calculating the heat of reaction ΔH for different reaction types
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