CHEM II EXAM II

Reaction Rate

Speed at which a reaction occurs.

Units of Reaction Rate

M/s, mol/hr, g/s, mol/L-hr.

Factors Affecting Reaction Rates

1. Physical State of Reactants 2. Reactant Concentration 3. Temperature 4. Catalysts.

Effect of Concentration on Reaction Rate

Higher concentration leads to more collisions and a faster reaction.

Effect of Temperature on Reaction Rate

Higher temperature results in a faster reaction rate.

Effect of Catalysts on Reaction Rate

Catalysts speed up reactions without being consumed.

Rate Law Formula

Rate = k[A]^m[B]^n, where m and n are the orders of reaction.

Overall Order of Reaction

Sum of the powers (m+n) in the rate law.

Units of Rate Constant (k) for Zero-order

M/s or mol L−1s−1.

Units of Rate Constant (k) for First-order

s−1.

Units of Rate Constant (k) for Second-order

L mol−1s−1.

Units of Rate Constant (k) for Third-order

L^2mol−2s−1.

First-Order Reaction Rate Law

Rate = k[A], with units of k as s−1.

Half-Life of a First-Order Reaction

t1/2 = 0.693/k.

Concentration Equation for a First-Order Reaction

ln[A] = ln[A]0 - kt.

Second-Order Reaction Rate Law

Rate = k[A]^2, with units of k as L mol−1s−1.

Half-Life of a Second-Order Reaction

t1/2 = 1/(k[A]0).

Zero-Order Reaction Rate Law

Constant rate, independent of reactant concentration.

Units of Rate Constant (k) for Zero-Order

M/s or mol L−1s−1.

Activation Energy

Energy required for reactants to reach the transition state.

Arrhenius Equation

k = Ae^(-Ea/RT), where A is the frequency factor.

Logarithmic Form of Arrhenius Equation

ln k = ln A - Ea/RT.

Molecularity

Refers to the number of molecules involved in an elementary step.

Equilibrium Constant (K) Formula

K = [products]^coefficients/[reactants]^coefficients.

Magnitude of Equilibrium Constant (K) when K > 1

Reaction favors products.

Magnitude of Equilibrium Constant (K) when K < 1

Reaction favors reactants.

Relationship Between Kp and Kc

Kp = Kc(RT)^Δn, where Δn is the change in moles.