For an ideal gas, heat absorbed in an isochoric process is equal to
A work done
B change in enthalpy
C change in internal energy
D zero
At constant volume, no work is done (W = 0), so q = ΔU.
In an adiabatic process, which quantity remains constant
A temperature
B pressure
C heat
D internal energy
In adiabatic process, q = 0 (no heat exchange).
Which of the following is a state function
A heat
B work
C internal energy
D path length
State functions depend only on initial and final states, not on path.
For a spontaneous process at constant temperature and pressure
A ΔH must be negative
B ΔS must be positive
C ΔG must be negative
D ΔU must be zero
Gibbs free energy criterion governs spontaneity at constant T and P.
If ΔH < 0 and ΔS < 0, the reaction is spontaneous at
A all temperatures
B high temperatures
C low temperatures
D no temperature
ΔG = ΔH − TΔS. When both are negative, low T keeps ΔG negative.
If ΔH > 0 and ΔS > 0, reaction is spontaneous at
A low temperatures
B high temperatures
C all temperatures
D never
Large TΔS term overcomes positive ΔH at high temperature.
If ΔH < 0 and ΔS > 0, reaction is
A spontaneous at all temperatures
B spontaneous at high temperature only
C spontaneous at low temperature only
D never spontaneous
Both factors favor spontaneity → ΔG always negative.
Entropy is a measure of
A energy
B disorder
C enthalpy
D heat content
Entropy measures randomness or disorder in a system.
Entropy change is maximum when a substance
A melts
B vaporizes
C solidifies
D condenses
Gas has maximum disorder compared to liquid and solid.
Which process has maximum increase in entropy
A solid → liquid
B liquid → gas
C gas → liquid
D solid → solid
Liquid to gas transition greatly increases randomness.
For reaction N₂ + 3H₂ ⇌ 2NH₃, Δn is
A −2
B +2
C −1
D +1
Δn = gaseous products − gaseous reactants = 2 − 4 = −2.
If Kp = 10 and Δn = −2 at 300 K, then Kc is
A less than Kp
B greater than Kp
C equal to Kp
D zero
Kp = Kc(RT)^Δn. With Δn negative, Kc > Kp.
Value of equilibrium constant depends on
A initial concentration
B catalyst
C temperature
D pressure
Equilibrium constant changes only with temperature.
Addition of catalyst to equilibrium mixture
A shifts equilibrium forward
B shifts equilibrium backward
C does not change equilibrium position
D changes equilibrium constant
Catalyst speeds up both forward and backward reactions equally.
If K = 1, equilibrium mixture contains
A mostly reactants
B mostly products
C comparable amounts of reactants and products
D no reactants
K = 1 indicates neither side is strongly favored.
For exothermic reaction, increase in temperature shifts equilibrium
A forward
B backward
C no change
D stops reaction
Heat acts as a product; increasing T favors reverse reaction.
Which change increases yield of NH₃ in Haber process
A high temperature
B low pressure
C high pressure
D removing catalyst
Reaction produces fewer moles of gas; high pressure favors products.
If reaction quotient Q = K, system is
A moving forward
B moving backward
C at equilibrium
D unstable
When Q equals K, no net reaction occurs.
For equilibrium reaction, increasing concentration of reactant
A decreases K
B increases K
C shifts equilibrium forward
D shifts equilibrium backward
System consumes added reactant to re-establish equilibrium.
Which factor does NOT affect equilibrium position
A temperature
B pressure
C catalyst
D concentration
Catalyst does not alter equilibrium composition.
pH of 0.01 M HCl is
A 1
B 2
C 3
D 4
Strong acid → [H⁺] = 10⁻² → pH = 2.
pH of 0.001 M NaOH is
A 11
B 12
C 13
D 14
0.001 M NaOH → [OH⁻] = 10⁻³ → pOH = 3 → pH = 11
Which is a weak acid
A HCl
B HNO₃
C CH₃COOH
D H₂SO₄
Acetic acid partially ionizes → weak acid.
Which salt gives basic solution in water
A NH₄Cl
B NaCl
C Na₂CO₃
D KCl
Salt of strong base and weak acid → basic solution.
For a weak acid, pH increases when
A Ka increases
B concentration decreases
C temperature decreases
D pressure increases
Dilution reduces [H⁺], increasing pH.
Which pair forms acidic buffer
A NH₄OH + NH₄Cl
B CH₃COOH + CH₃COONa
C NaOH + NaCl
D HCl + NaCl
Weak acid + its salt → acidic buffer.
pH of buffer depends on
A amount of solvent
B temperature only
C ratio of salt to acid
D pressure
Henderson equation shows pH depends on [salt]/[acid].
If Ka of an acid is 10⁻⁵, pKa is
A 3
B 4
C 5
D 6
pKa = −log Ka = 5.
Larger pKa means acid is
A stronger
B weaker
C neutral
D amphoteric
Higher pKa → smaller Ka → weaker acid.
The salt having least solubility has
A highest Ksp
B lowest Ksp
C Ksp = 1
D Ksp = 0
Lower Ksp → lower solubility.
Component is defined as
A number of phases
B minimum number of independent species
C total moles present
D total mass present
Components are chemically independent species needed to define system.
Water system is a
A one-component system
B two-component system
C three-component system
D four-component system
Ice, water, and vapor are all H₂O.
Degrees of freedom represent number of
A phases
B components
C variables that can be changed independently
D reactions
F indicates independent intensive variables.
In one-component system at triple point
A F = 1
B F = 2
C F = 0
D F = 3
Triple point is invariant.
The phase diagram of water shows negative slope of fusion curve because
A ice is denser than water
B water is denser than ice
C vapor is denser
D pressure has no effect
Increasing pressure favors liquid over solid.
At 1 atm, CO₂ does not exist in liquid state because
A critical pressure is high
B triple point pressure is above 1 atm
C boiling point is very low
D density is low
CO₂ triple point is at 5.1 atm.
Fusion curve represents equilibrium between
A solid and gas
B liquid and gas
C solid and liquid
D gas and gas
Fusion curve shows solid–liquid equilibrium.
Vapor pressure of a liquid increases with
A decrease in temperature
B increase in temperature
C increase in pressure
D decrease in volume
Higher temperature increases escaping tendency of molecules.
Boiling occurs when vapor pressure equals
A zero
B internal pressure
C atmospheric pressure
D critical pressure
At boiling point, vapor pressure equals external pressure.
Normal boiling point is boiling point at
A 0 atm
B 1 atm
C 2 atm
D critical pressure
Defined at standard atmospheric pressure.
Phase equilibrium involves equilibrium between
A chemical species
B physical states
C ions only
D electrons
Phase equilibrium deals with solid–liquid–gas transitions.
Which phase diagram has only one triple point
A CO₂
B water
C sulfur
D nitrogen
Water & CO₂ → one triple point
Sulfur → two triple points
Clapeyron equation relates
A pressure and volume
B temperature and entropy
C pressure and temperature during phase change
D energy and work
Clapeyron equation describes phase boundary slope.
Which transition shows no entropy change
A solid → liquid
B liquid → gas
C solid → gas
D ideal crystal at 0 K
Entropy is zero for perfect crystal at 0 K.
Gibbs free energy change for phase transition at equilibrium is
A positive
B negative
C zero
D infinite
At phase equilibrium, ΔG = 0.
Which factor shifts equilibrium constant
A pressure
B concentration
C temperature
D catalyst
K changes only with temperature.
When ΔG° is negative, equilibrium constant K is
A less than 1
B equal to 1
C greater than 1
D zero
ΔG° = −RT ln K → negative ΔG° implies K > 1.
For equilibrium reaction, ΔG at equilibrium is
A maximum
B minimum
C zero
D infinite
System has no driving force at equilibrium.
Increasing volume favors side with
A fewer gas moles
B more gas moles
C more solids
D no effect
Lower pressure favors more gaseous moles.
The equilibrium constant of reverse reaction is
A same as forward
B reciprocal of forward
C square of forward
D zero
K(reverse) = 1/K(forward)