physcial II (p1&2)

Question 1

What does a negative Gibbs Free Energy (ΔG) indicate?

Answer 1

A negative change in Gibbs Free Energy (ΔG<0) indicates that the reaction is spontaneous under the given conditions.

Question 2

What happens to the Gibbs Free Energy if both enthalpy (ΔH) and entropy (ΔS) are positive?

Answer 2

If both ΔH and ΔS are positive, the reaction will be spontaneous at high temperatures, because the TΔS term (which is positive) will outweigh the positive ΔH term.

Question 3

What is Gibbs Free Energy?

Answer 3

Gibbs Free Energy (G) is a thermodynamic quantity that combines enthalpy (H), temperature (T), and entropy (S) to predict the spontaneity of a reaction. The formula is:
G=ΔH−TΔS

Question 4

What does a positive Gibbs Free Energy (ΔGΔG) indicate?

Answer 4

A positive change in Gibbs Free Energy (ΔG>0) indicates that the reaction is non-spontaneous under the given conditions. The reaction will not occur without external input.

Question 5

What is the relationship between Gibbs Free Energy and spontaneity?

Answer 5

The spontaneity of a reaction is determined by the sign of the Gibbs Free Energy change (ΔG):
* ΔG<0: Spontaneous reaction.
* ΔG>0: Non-spontaneous reaction.
* ΔG=0: Reaction is at equilibrium.

Question 6

What is the relationship between Gibbs Free Energy and equilibrium constant (K)?

Answer 6

The standard Gibbs Free Energy change (ΔG) is related to the equilibrium constant (K) by the equation:
ΔG=−RTln⁡K

Question 7

What does it mean if the equilibrium constant (K) is greater than 1 in terms of Gibbs Free Energy?

Answer 7

If the equilibrium constant (K>1), the reaction is product-favored, and ΔG is negative, meaning the reaction is spontaneous under standard conditions.

Question 8

What does it mean if the equilibrium constant (K) is less than 1 in terms of Gibbs Free Energy?

Answer 8

: If the equilibrium constant (K<1), the reaction is reactant-favored, and ΔG is positive, meaning the reaction is non-spontaneous under standard conditions.

Question 9

How does temperature affect the spontaneity of a reaction in relation to Gibbs Free Energy?

Answer 9

Temperature affects the spontaneity of a reaction because it influences the entropy term (TΔS) in the Gibbs Free Energy equation.
For a reaction to be spontaneous at high temperatures, ΔS must be positive, and at low temperatures, ΔH must be negative.

Question 10

What happens to the Gibbs Free Energy if both enthalpy (ΔH) and entropy (ΔS) are negative?

Answer 10

If both ΔH and ΔS are negative, the spontaneity of the reaction depends on the temperature:
* At low temperatures, the negative ΔH term dominates, and the reaction may be spontaneous.
* At high temperatures, the negative ΔS term dominates, and the reaction may be non-spontaneous.

Question 11

What is an acid according to the Arrhenius definition?

Answer 11

An acid is a substance that increases the concentration of hydrogen ions (H⁺) or protons in aqueous solutions

Question 12

What is a base according to the Arrhenius definition?

Answer 12

A base is a substance that increases the concentration of hydroxide ions (OH⁻) in aqueous solutions.

Question 13

What is the Bronsted-Lowry definition of an acid

Answer 13

A Bronsted-Lowry base is a proton (H⁺) acceptor.

Question 14

What is the pH scale?

Answer 14

The pH scale measures the acidity or alkalinity of a solution. It is a scale from 0 to 14, where pH 7 is neutral, pH < 7 is acidic, and pH > 7 is alkaline.

Question 15

What is the relationship between hydrogen ion concentration and pH?

Answer 15

pH = -log[H⁺], where [H⁺] is the concentration of hydrogen ions in mol/L.

Question 16

What is a strong acid?

Answer 16

A strong acid is an acid that completely dissociates in water, releasing all of its hydrogen ions.

Question 17

What is a weak acid?

Answer 17

A weak acid is an acid that only partially dissociates in water, releasing only a small proportion of its hydrogen ions.

Question 18

What is a strong base?

Answer 18

A strong base is a base that completely dissociates in water to release hydroxide ions (OH⁻).

Question 19

What is a weak base?

Answer 19

A weak base is a base that only partially dissociates in water, releasing a small proportion of hydroxide ions.

Question 20

What is the dissociation constant (Ka) for a weak acid?

Answer 20

Ka is the equilibrium constant for the dissociation of a weak acid in water:
HA ⇌ H⁺ + A⁻
Ka = [H⁺][A⁻] / [HA], where [HA] is the concentration of the undissociated acid.

Question 21

What is the dissociation constant (Kb) for a weak base?

Answer 21

Kb is the equilibrium constant for the dissociation of a weak base in water:
B + H₂O ⇌ BH⁺ + OH⁻
Kb = [BH⁺][OH⁻] / [B], where [B] is the concentration of the undissociated base.

Question 22

What is the pKa of an acid?

Answer 22

The pKa is the negative logarithm of the acid dissociation constant (Ka):
pKa = -log(Ka).
The lower the pKa, the stronger the acid.

Question 23

What is the pKb of a base?

Answer 23

The pKb is the negative logarithm of the base dissociation constant (Kb):
pKb = -log(Kb).
The lower the pKb, the stronger the base.

Question 24

What is a buffer solution?

Answer 24

A buffer solution is a solution that resists changes in pH when small amounts of acid or base are added. It typically contains a weak acid and its conjugate base, or a weak base and its conjugate acid.

Question 25

What is an acid-base titration?

Answer 25

An acid-base titration is a method used to determine the concentration of an acid or base by neutralizing it with a base or acid of known concentration, using an indicator to identify the endpoint.

Question 26

What is the equivalence point in an acid-base titration?

Answer 26

The equivalence point is the point at which the amount of acid is stoichiometrically equivalent to the amount of base in the solution, and the reaction is complete.

Question 27

What is the role of an indicator in an acid-base titration?

Answer 27

An indicator is a substance that changes color at a specific pH range, signaling the endpoint of the titration.

Question 28

What is a rate equation?

Answer 28

A rate equation shows the relationship between the rate of a chemical reaction and the concentrations of the reactants. It is usually written as:
Rate = k[A]^m[B]^n,
where k is the rate constant, [A] and [B] are the concentrations of reactants, and m and n are their respective orders.

Question 29

What is the rate constant (k)?

Answer 29

The rate constant (k) is a proportionality constant that links the rate of a reaction to the concentrations of reactants in the rate equation. It is specific to a reaction at a given temperature and has units that depend on the overall order of the reaction.

Question 30

What is the order of a reaction with respect to a reactant?

Answer 30

The order of reaction with respect to a reactant (e.g., m in Rate = k[A]^m) refers to the power to which the concentration of the reactant is raised in the rate equation. It indicates how the rate changes as the concentration of that reactant changes.

Question 31

What is a rate-determining step?

Answer 31

The rate-determining step is the slowest step in a reaction mechanism, which determines the overall rate of the reaction. It is the step with the highest activation energy.