AP CHEM Unit 5 Day 1 Review

Front

What is the process of dissolving NaCl(s) in water, and how does it affect entropy?

Back

The process of dissolving NaCl(s) in water results in the formation of Na⁺(aq) and Cl⁻(aq) ions, which increases the entropy of the system due to the greater disorder in the aqueous state compared to the solid state.

Front

What are the signs of ΔH, ΔS, and ΔG for the freezing of water at −10°C and 1 atm?

Back

For the freezing of water at −10°C and 1 atm, the signs are: ΔH is negative (−ΔH), ΔS is negative (−ΔS), and ΔG is negative (−ΔG).

Front

What does a positive ΔS value indicate about a chemical reaction?

Back

A positive ΔS value indicates that the disorder of the system is increasing, often associated with the formation of gases from solids or liquids, as in the reaction H₂(g) + I₂(s) → 2 HI(g).

Front

How do you calculate the standard free-energy change (ΔG°) for a reaction?

Back

The standard free-energy change (ΔG°) can be calculated using the equation ΔG° = ΔH° - TΔS°, where ΔH° is the standard enthalpy change, T is the temperature in Kelvin, and ΔS° is the standard entropy change.

Front

What does a negative ΔG indicate about a chemical reaction?

Back

A negative ΔG indicates that the reaction is spontaneous under standard conditions, meaning it can proceed without the input of additional energy.

Front

What is the equilibrium constant (Kc) and what does it signify in a chemical reaction?

Back

The equilibrium constant (Kc) is a numerical value that expresses the ratio of the concentrations of products to reactants at equilibrium. A large Kc indicates that products are favored, while a small Kc indicates that reactants are favored.

Front

What is the relationship between ΔG and the direction of a reaction?

Back

The relationship is as follows: if ΔG < 0, the reaction proceeds forward; if ΔG > 0, the reaction is non-spontaneous in the forward direction; and if ΔG = 0, the system is at equilibrium.

Front

What is the significance of the standard state in thermodynamics?

Back

The standard state refers to the reference conditions (1 atm pressure, 25°C) used to measure thermodynamic properties, allowing for consistent comparisons between different substances.

Front

How does temperature affect the spontaneity of a reaction?

Back

Temperature can affect spontaneity through the term TΔS in the Gibbs free energy equation. An increase in temperature can make a reaction spontaneous if ΔS is positive.

Front

What is the difference between enthalpy (ΔH) and entropy (ΔS)?

Back

Enthalpy (ΔH) is a measure of the total heat content of a system, while entropy (ΔS) is a measure of the disorder or randomness in a system.