Thermochemistry and Energy Flashcards
6 cards from real CART practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Thermochemistry and Energy flashcards as text
What is the term for the heat released or absorbed during a chemical reaction at constant pressure?
Answer: Enthalpy change (ΔH)
Enthalpy change (ΔH) represents the heat flow in a reaction carried out at constant pressure.
A reaction with a negative ΔH value is classified as:
Answer: Exothermic
A negative ΔH means the system releases heat to the surroundings, making the reaction exothermic.
Which law states that the enthalpy of a reaction is the same whether it occurs in one step or multiple steps?
Answer: Hess's Law
Hess's Law states that total enthalpy change is path-independent and can be calculated by adding individual step enthalpies.
The specific heat capacity of water is 4.18 J/(g·°C). How much heat is needed to raise 50 g of water by 10°C?
Answer: 2090 J
Using q = mcΔT: q = 50 g × 4.18 J/(g·°C) × 10°C = 2090 J.
Which of the following processes is endothermic?
Answer: Melting of ice
Melting requires heat input to break intermolecular forces, making it an endothermic process.
Standard enthalpy of formation (ΔH°f) for an element in its standard state is:
Answer: 0 kJ/mol
By definition, the standard enthalpy of formation of any element in its most stable standard state is exactly zero.