CHEM 153A Midterm 1 Exam {fall 2025/26
Update} Questions and Complete Solutions –
UCLA.
Nonpolar amino acids - correct answer Glycine, alanine, valine, leucine, isoleucine,
methionine, proline
Polar amino acids - correct answer Serine, threonine, asparagine, glutamine, cysteine
Positively charged (basic) amino acids - correct answer Lysine, arginine, histidine
Negatively charged (acidic) amino acids - correct answer Aspartic acid, glutamic acid
Aromatic amino acids - correct answer Phenylalanine, tryptophan, tyrosine
Basic components of an amino acid - correct answer Carboxylate, ammonia, alpha
carbon, R group, alpha hydrogen
What does ∆G tell us - correct answer What can happen, not the rate
Direction of reaction
Exothermic reaction - correct answer Release more energy from forming stronger
bonds than put in to break weaker bonds
Endothermic reaction - correct answer Require more energy to break stronger bonds
than released from forming weaker bonds
, CHEM 153A Midterm 1 Exam {fall 2025/26
Update} Questions and Complete Solutions –
UCLA.
What entropy is favorable? - correct answer +∆S
What enthalpy is favorable? - correct answer -∆H (more energy released than
required)
What ∆G is favorable? - correct answer -∆G (spontaneous)
Equilibrium - correct answer Closed system
A-->B and B-->A at same rate
Steady state - correct answer Open system
Equal rates of input and output of the system
Equilibrium ∆Gº' = - correct answer -RT ln(Keq)
Steady-state ∆Gº' = - correct answer -RT ln(Keq)
Steady-state (A-->B) ∆Gº' = - correct answer -RT ln(Keq)
∆Gº' - correct answer Standard temperature, pressure, pH = 7, at equilibrium
, CHEM 153A Midterm 1 Exam {fall 2025/26
Update} Questions and Complete Solutions –
UCLA.
Equilibrium ∆G = - correct answer 0
Steady state ∆G = - correct answer ∆Gº' + RT ln(Q)
≠0
Steady state (A-->B) ∆G = - correct answer < 0
Equilibrium ratio [B]/[A] - correct answer = Keq
Steady state ratio [B]/[A] - correct answer = Q
Q ≠ Keq
Steady state (A-->B) ratio [B]/[A] - correct answer = Q
Q < Keq
Equilibrium rate of change of [A] and [B] - correct answer = 0
Steady state rate of change of [A] and [B] - correct answer = 0
Steady state (A-->B) rate of change of [A] and [B] - correct answer = 0
, CHEM 153A Midterm 1 Exam {fall 2025/26
Update} Questions and Complete Solutions –
UCLA.
Equilibrium rate of forward reaction vs rate of reverse reaction - correct answer f(f) =
f(b)
Steady state rate of forward reaction vs rate of reverse reaction - correct answer f(f) ≠
f(b)
Steady state (A-->B) rate of forward reaction vs rate of reverse reaction - correct
answer f(f) ≠ f(b)
Equilibrium rate in vs rate out - correct answer 0 (doesn't exist)
Steady state rate in vs rate out - correct answer f(in) = f(out)
Steady state (A-->B) rate in vs rate out - correct answer f(in) = f(out)
Keq vs Q - correct answer Keq = [products]/[reactants] at equilibrium
Q = [products]/[reactants] at any point
What do steady state and equilibrium have in common? - correct answer Reactants
and products are continuously being made
Concentrations of reactants and products are unchanging
Update} Questions and Complete Solutions –
UCLA.
Nonpolar amino acids - correct answer Glycine, alanine, valine, leucine, isoleucine,
methionine, proline
Polar amino acids - correct answer Serine, threonine, asparagine, glutamine, cysteine
Positively charged (basic) amino acids - correct answer Lysine, arginine, histidine
Negatively charged (acidic) amino acids - correct answer Aspartic acid, glutamic acid
Aromatic amino acids - correct answer Phenylalanine, tryptophan, tyrosine
Basic components of an amino acid - correct answer Carboxylate, ammonia, alpha
carbon, R group, alpha hydrogen
What does ∆G tell us - correct answer What can happen, not the rate
Direction of reaction
Exothermic reaction - correct answer Release more energy from forming stronger
bonds than put in to break weaker bonds
Endothermic reaction - correct answer Require more energy to break stronger bonds
than released from forming weaker bonds
, CHEM 153A Midterm 1 Exam {fall 2025/26
Update} Questions and Complete Solutions –
UCLA.
What entropy is favorable? - correct answer +∆S
What enthalpy is favorable? - correct answer -∆H (more energy released than
required)
What ∆G is favorable? - correct answer -∆G (spontaneous)
Equilibrium - correct answer Closed system
A-->B and B-->A at same rate
Steady state - correct answer Open system
Equal rates of input and output of the system
Equilibrium ∆Gº' = - correct answer -RT ln(Keq)
Steady-state ∆Gº' = - correct answer -RT ln(Keq)
Steady-state (A-->B) ∆Gº' = - correct answer -RT ln(Keq)
∆Gº' - correct answer Standard temperature, pressure, pH = 7, at equilibrium
, CHEM 153A Midterm 1 Exam {fall 2025/26
Update} Questions and Complete Solutions –
UCLA.
Equilibrium ∆G = - correct answer 0
Steady state ∆G = - correct answer ∆Gº' + RT ln(Q)
≠0
Steady state (A-->B) ∆G = - correct answer < 0
Equilibrium ratio [B]/[A] - correct answer = Keq
Steady state ratio [B]/[A] - correct answer = Q
Q ≠ Keq
Steady state (A-->B) ratio [B]/[A] - correct answer = Q
Q < Keq
Equilibrium rate of change of [A] and [B] - correct answer = 0
Steady state rate of change of [A] and [B] - correct answer = 0
Steady state (A-->B) rate of change of [A] and [B] - correct answer = 0
, CHEM 153A Midterm 1 Exam {fall 2025/26
Update} Questions and Complete Solutions –
UCLA.
Equilibrium rate of forward reaction vs rate of reverse reaction - correct answer f(f) =
f(b)
Steady state rate of forward reaction vs rate of reverse reaction - correct answer f(f) ≠
f(b)
Steady state (A-->B) rate of forward reaction vs rate of reverse reaction - correct
answer f(f) ≠ f(b)
Equilibrium rate in vs rate out - correct answer 0 (doesn't exist)
Steady state rate in vs rate out - correct answer f(in) = f(out)
Steady state (A-->B) rate in vs rate out - correct answer f(in) = f(out)
Keq vs Q - correct answer Keq = [products]/[reactants] at equilibrium
Q = [products]/[reactants] at any point
What do steady state and equilibrium have in common? - correct answer Reactants
and products are continuously being made
Concentrations of reactants and products are unchanging
