This set of Physical Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Phase Equilibrium”.
1. Calculate the work performed when 2 moles of hydrogen expand isothermally and reversibly at 25℃ from 15 to 50 litres.
a) 1436 calories
b) 1562 calories
c) -1436 calories
d) -1562 calories
View Answer
Explanation: W = -2.303 n RT log (V2 / V1) = -2.303 * 2 * 2 * 298 * log (50/15) = -1436 calories.
2. Phase transitions usually take place at constant temperature.
a) True
b) False
View Answer
Explanation: Phase transitions usually takes place at constant pressure and constant temperature. So, ΔT = 0. But still, ΔH and ΔT are non-zero.
3. What is the limitation of First law of thermodynamics?
a) It cannot predict the speed
b) It cannot predict the direction
c) It cannot predict nature
d) It cannot predict the temperature
View Answer
Explanation: The first law of thermodynamics cannot predict the direction of any process. But in nature, a process is found to have a specific direction for certain conditions.
4. What is the relation between energy and enthalpy of a reaction?
a) CPig / R
b) CP / R
c) ΔH = Δr U + (ΔVg) RT
d) (CVig / R) = (CPig / R) – 1
View Answer
Explanation: The relation between energy and enthalpy of reaction is ΔH = Δr U + (ΔVg) RT, where ΔVg is the change in the stoichiometric number of gaseous species in going from reactants to products. While calculating ΔVg of a reaction, only the stoichiometric number of gaseous is counted and those of liquids and solids are completely ignored.
5. How can you measure Enthalpy of Combustion?
a) Pressure gauge
b) Mercury Thermometer
c) Flowmeter
d) Bomb Calorimeter
View Answer
Explanation: Enthalpy of Combustion is usually measured by placing a known mass of the compound in a closed steel container (known as Bomb Calorimeter) which is filled with oxygen at about 30 bar pressures.
6. What is Bond enthalpy?
a) It is a particular state of species at specified conditions
b) When a system is in contact with an outside thermal reservoir, the change will occur slowly
c) It is the average of enthalpies required to dissociate the bond
d) A reaction which forms a single compound from its constituent elements
View Answer
Explanation: The bond enthalpy is the average of enthalpies required to dissociate the said bond present in different gaseous compounds into free atoms or radicals in the gaseous state.
7. Which one of these is not an intensive property?
a) Boiling point
b) pH
c) e.m.f of a cell
d) Entropy
View Answer
Explanation: Thermodynamic entropy is an extensive property. It has scales with size or extent of the system.
8. The feasibility of reaction cannot be determined by thermodynamics.
a) True
b) False
View Answer
Explanation: The primary objective of thermodynamics is to predict the feasibility of the reaction or the spontaneity of the given transformation.
9. What is the use of Clausius Clapeyron equation?
a) Predict boiling behavior
b) Predict melting point
c) Predict the amount of heat transferred
d) Predict the pressure
View Answer
Explanation: The Clausius Clapeyron equation allows one to predict the boiling behavior of a given pure substance. Any point on the pressure vapor curve can be chosen as reference.
10. What is the Clausius Clapeyron equation?
a) V = n V10
b) ln(p/p0) = Δv H/R*(1/T0 – 1/T)
c) V = n V1 + n V2
d) ln(p/p0) = Δv
View Answer
Explanation: This is Clausius Clapeyron equation ln(p/p0) = Δv H/R*(1/T0 – 1/T). It allows to predict the boiling behavior of any substance. It relates the slope of a reaction line to the fundamental thermodynamic properties.
Sanfoundry Global Education & Learning Series – Physical Chemistry.
To practice all areas of Physical Chemistry, here is complete set of Multiple Choice Questions and Answers.
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