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Questions and Answers
The formula for heat flow is q = ____ x ∆t.
The formula for heat flow is q = ____ x ∆t.
C
What does C stand for in the formula q = C x ∆t?
What does C stand for in the formula q = C x ∆t?
Heat capacity (J/ºC)
In the formula q = m x c x ∆t, m stands for ____.
In the formula q = m x c x ∆t, m stands for ____.
mass
What does c represent in the heat flow equation q = m x c x ∆t?
What does c represent in the heat flow equation q = m x c x ∆t?
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What is the specific heat of H₂O?
What is the specific heat of H₂O?
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The equation q reaction = -q calorimeter represents the heat flow for the reaction system.
The equation q reaction = -q calorimeter represents the heat flow for the reaction system.
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What does the equation q reaction = -C cal x ∆t represent?
What does the equation q reaction = -C cal x ∆t represent?
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What does Hess's law state according to the formula ∆H = ∆H₁ + ∆H₂?
What does Hess's law state according to the formula ∆H = ∆H₁ + ∆H₂?
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According to the equation q reaction at constant pressure = ∆H, what does ∆H represent?
According to the equation q reaction at constant pressure = ∆H, what does ∆H represent?
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What formula is used to determine standard enthalpy change?
What formula is used to determine standard enthalpy change?
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The law of conservation of energy can be expressed as ∆E system = -∆E surroundings.
The law of conservation of energy can be expressed as ∆E system = -∆E surroundings.
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What does the first law of thermodynamics state in relation to the equation ∆E = q + w?
What does the first law of thermodynamics state in relation to the equation ∆E = q + w?
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How is heat flow at constant pressure expressed mathematically?
How is heat flow at constant pressure expressed mathematically?
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How is heat flow at constant volume expressed mathematically?
How is heat flow at constant volume expressed mathematically?
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What does the equation ∆H = ∆E + ∆(PV) represent?
What does the equation ∆H = ∆E + ∆(PV) represent?
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In the equation ∆H = ∆E + ∆ngRT, what does R represent?
In the equation ∆H = ∆E + ∆ngRT, what does R represent?
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Study Notes
Thermochemistry Formulas
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Heat Capacity Formula: ( q = C \times \Delta t )
- ( C ) represents heat capacity in Joules per degree Celsius (J/ºC).
- ( \Delta t ) is the change in temperature computed as final temperature minus initial temperature.
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Heat Flow Formula: ( q = m \times c \times \Delta t )
- ( m ) stands for mass, ( c ) is the specific heat, and ( \Delta t ) is the temperature change.
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Specific Heat of Water:
- Water has a specific heat of 4.18 J/gºC, essential for calculations involving heat transfer.
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Heat Transfer in Reactions:
- The relationship ( q_{\text{reaction}} = -q_{\text{calorimeter}} ) indicates that the heat exchanged by the reaction is equal in magnitude but opposite in sign to the heat measured in the calorimeter.
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Bomb Calorimeter Equation:
- ( q_{\text{reaction}} = -C_{cal} \times \Delta t ) can determine the heat absorbed or released in a reaction using known calorimeter heat capacity and temperature change.
Thermodynamic Laws and Relationships
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Hess's Law:
- ( \Delta H = \Delta H_1 + \Delta H_2 ) asserts that the total enthalpy change for a reaction is the sum of the changes for individual steps.
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Enthalpy Change at Constant Pressure:
- ( q_{\text{reaction}} ) at constant pressure equals ( \Delta H ), where ( \Delta H ) is the difference in enthalpy between products and reactants.
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Standard Enthalpy Change:
- Calculated using the formula ( \Delta H^\circ = \sum \Delta H^\circ_f \text{(products)} - \sum \Delta H^\circ_f \text{(reactants)} ).
Energy Conservation Principles
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Conservation of Energy:
- The equation ( \Delta E_{\text{system}} = -\Delta E_{\text{surroundings}} ) embodies the principle that energy lost by one system is gained by another.
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First Law of Thermodynamics:
- Expressed as ( \Delta E = q + w ) where total energy change equals the sum of heat flow and work done.
Enthalpy Relationships
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Heat Flow and Enthalpy:
- At constant pressure, ( \Delta H = q_p ) shows that heat flow is directly related to changes in enthalpy.
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Constant Volume Heat Flow:
- At constant volume, ( \Delta H = q_v ) still maintains a direct relationship between heat flow and enthalpy.
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Change in Enthalpy and Energy:
- ( \Delta H = \Delta E + \Delta(PV) ) links changes in enthalpy to changes in energy and the product of pressure and volume.
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Relation between Enthalpy and Energy Change:
- ( \Delta H = \Delta E + \Delta n_g RT ) describes how enthalpy change correlates to energy change plus adjustments for changes in gas moles at temperature ( T ), with R as the ideal gas constant (8.31 J/mol K).
Studying That Suits You
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Description
Test your knowledge of thermochemistry formulas with these flashcards. Each card presents essential equations and definitions, ranging from heat capacity to specific heat. Perfect for chemistry students looking to reinforce their understanding of heat flow and reactions.
