For an ideal gas, which quantity remains constant during an adiabatic process
A temperature
B pressure
C PVᵞ
D volume
In adiabatic process, no heat exchange occurs and the relation PVγ=constantPV^\gamma = \text{constant}PVγ=constant holds.
The value of γ (Cp/Cv) for a monoatomic ideal gas is
A 1.33
B 1.40
C 1.50
D 1.67
For monoatomic gases, γ = 5/3 ≈ 1.67.
Work done in free expansion of an ideal gas is
A maximum
B minimum
C zero
D infinite
In free expansion, external pressure is zero, so work done is zero.
Which process is thermodynamically reversible
A rapid expansion
B free expansion
C quasi-static process
D spontaneous combustion
Reversible processes occur infinitely slowly through equilibrium states.
Entropy change of universe for a reversible process is
A positive
B negative
C zero
D infinite
For reversible process, ΔS(system) + ΔS(surroundings) = 0.
For spontaneous process, entropy of universe
A decreases
B remains constant
C increases
D becomes zero
Second law states total entropy increases for spontaneous processes.
If ΔH = +40 kJ and ΔS = +100 J/K, reaction becomes spontaneous above
A 200 K
B 300 K
C 400 K
D 500 K
ΔG = ΔH − TΔS
Set ΔG = 0 → T = ΔH/ΔS = 40000/100 = 400 K.
At equilibrium, Gibbs free energy is
A maximum
B minimum
C zero always
D infinite
At equilibrium, G is minimum though ΔG = 0.
Which thermodynamic quantity predicts direction of reaction at constant T and P
A ΔH
B ΔS
C ΔU
D ΔG
Gibbs free energy change determines spontaneity at constant T and P.
The unit of Gibbs free energy change is
A J
B J/K
C J/mol
D J/mol•K
Free energy change is expressed per mole.
For reaction A ⇌ B, K = 10. At equilibrium, concentration ratio [B]/[A] is
A 0.1
B 1
C 10
D 100
K = [B]/[A] = 10.
Which change does NOT alter equilibrium constant
A temperature
B pressure
C catalyst
D nature of reaction
Catalyst does not change K, only rate.
For an equilibrium reaction, increasing concentration of products will
A increase K
B decrease K
C shift equilibrium backward
D stop reaction
System counteracts change by consuming products.
If equilibrium constant is very small, reaction favors
A products
B reactants
C equal amounts
D catalysts
Small K means equilibrium lies far to reactant side.
Which factor affects both equilibrium constant and equilibrium position
A pressure
B concentration
C temperature
D catalyst
Temperature changes both K and position of equilibrium.
For N₂ + 3H₂ ⇌ 2NH₃, increasing volume shifts equilibrium
A forward
B backward
C no change
D equilibrium disappears
Increase in volume (decrease in pressure) favors side with more moles (reactants).
If reaction quotient Q = 0, system will
A be at equilibrium
B move backward
C move forward
D stop reacting
No products present → reaction proceeds forward to form products.
Which equilibrium constant expression ignores solids
A Kc
B Kp
C Ksp
D all equilibrium constants
Activities of pure solids and liquids are taken as unity.
Equilibrium constant is dimensionless because
A it has no unit
B activities are unitless
C pressure cancels out
D volume cancels out
K is written in terms of activities, which are dimensionless.
For equilibrium reaction, ΔG° is related to K as
A ΔG° = RT ln K
B ΔG° = −RT ln K
C ΔG° = RT/K
D ΔG° = −RT/K
This relation links thermodynamics and equilibrium.
pH of 10⁻⁸ M HCl solution is approximately
A 6
B 7
C 8
D 5
Very dilute acid → contribution of water dominates → pH ≈ 7.
Which solution has highest pH
A 0.1 M HCl
B 0.01 M NaOH
C 0.001 M NH₄Cl
D pure water
Strong base gives highest pH.
Which salt solution is acidic
A Na₂CO₃
B NH₄Cl
C NaCl
D KNO₃
Salt of weak base and strong acid gives acidic solution.
Which salt solution is basic
A NH₄Cl
B NaCl
C Na₂CO₃
D KCl
Salt of strong base and weak acid produces basic solution.
Buffer capacity depends on
A absolute pH
B temperature only
C concentration of buffer components
D pressure
Higher concentrations provide greater resistance to pH change.
Which will disturb buffer pH most
A dilution
B small addition of acid
C small addition of base
D change in pressure
Dilution reduces buffer concentration and capacity.
Which ion suppresses dissociation of CH₃COOH
A Na⁺
B Cl⁻
C CH₃COO⁻
D OH⁻
Common ion (acetate) shifts equilibrium backward.
For salt MX with Ksp = 4×10⁻⁸, molar solubility is
A 2×10⁻⁴
B 4×10⁻⁴
C 1×10⁻⁴
D 2×10⁻⁸
Ksp = s² → s = √(4×10⁻⁸) = 2×10⁻⁴.
Precipitation begins when
A Qsp = 0
B Qsp < Ksp
C Qsp = Ksp
D Qsp > Ksp
Supersaturation causes precipitation.
Selective precipitation is based on difference in
A pH
B Ksp values
C solubility
D temperature
Lower Ksp salt precipitates first.
Phase equilibrium is dynamic because
A phases stop changing
B forward and backward changes occur at equal rates
C system is static
D temperature is constant
Molecules continuously change phase but net change is zero.
In one-component system, maximum number of phases that can coexist is
A 2
B 3
C 4
D infinite
At triple point, solid, liquid and gas coexist.
Phase rule is applicable to
A only homogeneous systems
B only heterogeneous systems
C both homogeneous and heterogeneous systems
D chemical reactions only
Phase rule is general.
At constant pressure, degrees of freedom reduce by
A 0
B 1
C 2
D 3
Reduced phase rule: F = C − P + 1.
Reduced phase rule is applicable when
A temperature is constant
B pressure is constant
C volume is constant
D mass is constant
One variable (pressure) is fixed.
Water boils at lower temperature on hills because
A pressure increases
B pressure decreases
C density decreases
D temperature increases
Lower atmospheric pressure lowers boiling point.
In CO₂ phase diagram, liquid CO₂ exists only above
A critical temperature
B triple point pressure
C 1 atm pressure
D 0°C
Liquid CO₂ exists only above 5.1 atm.
Sublimation is transition from
A solid → liquid
B liquid → gas
C solid → gas
D gas → liquid
Direct solid-to-vapour transition.
Which phase diagram shows two triple points
A water
B carbon dioxide
C sulfur
D nitrogen
Sulfur has two solid allotropes → two triple points.
Chemical potential at equilibrium between phases is
A maximum
B minimum
C equal
D zero
Phase equilibrium requires equal chemical potential.
Vapour pressure of liquid becomes zero at
A boiling point
B melting point
C absolute zero
D critical point
At 0 K, no molecules escape into vapour.
Phase diagram is drawn between
A pressure and volume
B temperature and entropy
C pressure and temperature
D volume and temperature
Standard phase diagrams are P–T plots.
Ice floats on water because
A ice is denser
B water is denser
C ice is amorphous
D hydrogen bonding absent
Ice has open hydrogen-bonded structure → lower density.
At equilibrium, chemical potential of a substance is
A maximum
B minimum
C constant
D zero
No driving force exists when chemical potential is constant.
Which process shows no entropy change for universe
A spontaneous
B irreversible
C reversible
D explosive
For reversible process, ΔS_universe = 0.
Which statement is true
A entropy of universe decreases
B entropy of isolated system always increases
C entropy of isolated system never changes
D entropy is conserved
Second law of thermodynamics.
Which condition corresponds to chemical equilibrium
A ΔH = 0
B ΔS = 0
C ΔG = 0
D ΔU = 0
At equilibrium, Gibbs free energy change is zero.
The equilibrium constant of reaction at given temperature is
A affected by initial concentration
B affected by catalyst
C affected by temperature
D affected by pressure only
K depends only on temperature.
Phase equilibrium deals with
A chemical reactions
B nuclear reactions
C physical changes
D ionic reactions
It studies equilibrium between physical states.
For any spontaneous process at constant T and P, ΔG is
A zero
B positive
C negative
D infinite
Negative ΔG is the criterion of spontaneity.