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What is the difference between exothermic and endothermic reactions?
Exothermic: ΔH is negative, heat is released. Endothermic: ΔH is positive, heat is absorbed.
Differentiate between heat (q) and work (w).
Heat: Energy transfer due to temperature difference. Work: Energy transfer due to force over a distance.
What is the difference between Enthalpy (H) and Internal Energy (E)?
Enthalpy: Total energy of a system including pressure and volume. Internal Energy: Total kinetic and potential energy within a system.
What is the effect of a negative ΔH on the surroundings?
The surroundings get warmer (exothermic reaction).
What is the effect of a positive ΔH on the surroundings?
The surroundings get cooler (endothermic reaction).
What is the effect of heat being added to a system?
The internal energy of the system increases (q is positive).
What is the effect of work being done on a gas?
The internal energy of the gas increases (w is positive).
What is the effect of decreasing the number of moles of gas in a reaction at constant pressure?
Work is done by the system.
What is Enthalpy (H)?
The total energy of a system, including internal energy plus energy related to pressure and volume.
What is ΔH?
The change in enthalpy, representing heat flow in reactions or phase changes. ΔH = H<sub>final</sub> - H<sub>initial</sub>
What is ΔH<sub>rxn</sub>?
The heat absorbed or released during a chemical reaction.
Define an exothermic reaction.
A reaction where ΔH is negative, and heat is released by the system.
Define an endothermic reaction.
A reaction where ΔH is positive, and heat is absorbed by the system.
What is Energy (E)?
The ability to do work or transfer heat, measured in joules (J) or calories (cal).
What is Internal Energy (E or U)?
The total kinetic and potential energy within a system. ΔE = q + w
What is Heat (q)?
Energy transfer due to a temperature difference, flowing from hot to cold, measured in joules (J).
What is Work (w)?
Energy transfer due to a force acting over a distance. w = -PΔV