Chemistry: Thermodynamics & Thermochemistry Flashcards
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Read the first 7 Chemistry: Thermodynamics & Thermochemistry flashcards as text
What is the sign of ΔH for an endothermic reaction?
Answer: Positive
Endothermic reactions absorb heat, so ΔH is positive.
A 50.0 g sample of water (c = 4.18 J/g·°C) is heated from 20.0 °C to 30.0 °C. How much heat is absorbed?
Answer: 2090 J
q = mcΔT = 50.0 × 4.18 × 10.0 = 2090 J.
Which quantity is a state function?
Answer: Enthalpy
Enthalpy depends only on the state, not the path; heat and work are path-dependent.
According to Hess's law, the enthalpy change of a reaction depends on what?
Answer: Only the initial and final states
Hess's law states ΔH depends only on initial and final states, regardless of path.
What does a negative ΔG indicate about a process?
Answer: It is spontaneous
A negative Gibbs free energy change means the process is spontaneous.
In the equation ΔG = ΔH − TΔS, what does T represent?
Answer: Absolute temperature in kelvin
T is the absolute temperature in kelvin.
What is the standard enthalpy of formation of an element in its standard state?
Answer: Zero
By definition, the standard enthalpy of formation of a pure element in its standard state is zero.