Thermodynamic Systems & First Law — Practice Questions

Free NEET Chemistry multiple-choice questions on Thermodynamic Systems & First Law. Attempt each question and reveal the answer with a full explanation.

Which of the following describes a system that can exchange energy but not matter with its surroundings? Closed system Open system Isolated system Adiabatic system Three moles of an ideal gas expanded spontaneously into vacuum. The work done will be: Zero Infinite 3 , J 9 , J Which of the following is a state function? Enthalpy Heat Work All of these Under isothermal conditions, for a reversible expansion of an ideal gas, the value of U is: 0 q w "q + w" Which of the following is the correct representation for the First Law of Thermodynamics for an isochoric process? U = q U = w q = -w U = 0 Which of the following is not an intensive property? Mass Pressure Temperature Density In a bomb calorimeter, the heat measured is: U H w q p Which of the following is true for an isolated system? q = 0, w = 0, U = 0 q 0, w = 0, U 0 q = 0, w 0, U = 0 q 0, w 0, U = 0 During an isothermal expansion of an ideal gas, which of the following remains constant? Internal energy Pressure Volume Entropy The intensive property among the following is: Specific heat capacity Mass Volume Enthalpy For which of the following processes is the work done zero? Isochoric process Isobaric process Isothermal process Cyclic process The ratio of two extensive properties results in: An intensive property An extensive property A state function always A path function always If 100 , kJ of heat is added to a system while the system does 60 , kJ of work, the change in internal energy is: 40 , kJ 160 , kJ -40 , kJ -160 , kJ Standard state of bromine at 298 , K and 1 , atm is: Br 2(l) Br 2(g) Br 2(s) Br(g) The internal energy of 1 , mole of an ideal gas depends only on: Temperature Pressure Volume Number of molecules For a cyclic process, which of the following is true? dU = 0 dq = 0 dw = 0 dV 0 In a cyclic process, the heat absorbed by the system is 100 , J and the work done BY the system is 100 , J . What is the change in internal energy ( U )? 0 , J 200 , J -200 , J 100 , J In the chemistry convention for the First Law of Thermodynamics ( U = q + w ), what does a positive value of w represent? Work is done ON the system by the surroundings. Work is done BY the system on the surroundings. Heat is absorbed by the system. The system is expanding. Hess's Law of Constant Heat Summation is based on the fact that Enthalpy is a: State function Path function Intensive property Colligative property If w is the work done by the system and q is the heat absorbed by the system, then the change in internal energy ( U ) for an adiabatic process is: -w q w q+w Which of the following describes the relationship between temperature ( T ) and volume ( V ) for an ideal gas during a reversible adiabatic process? TV -1 = constant T V = constant TV = constant T/V -1 = constant What is the work done (in Joules) when 1 , mole of an ideal gas expands from 10 , L to 20 , L at 300 , K against a constant external pressure of 1 , atm ? -1013.2 , J -10.0 , J -2026.4 , J +1013.2 , J Calculate the work done when 1 , mole of an ideal gas expands into an evacuated container (vacuum) of 10 , L from a 5 , L container at 300 , K . 0 , J 100 , J -2.303 RT 2 P V In an adiabatic process, no heat is exchanged with the surroundings. For this process, which is correct? q = 0 U = 0 w = 0 T = 0 Which of the following is an intensive property? Specific heat capacity Enthalpy Entropy Volume Calculate the work done (in Joules) by 1 , mol of an ideal gas when it expands from 5 , L to 10 , L into vacuum. 0 5 , J 10 , J 500 , J Which law states that if a system A is in thermal equilibrium with system B, and B is in thermal equilibrium with C, then A and C are also in thermal equilibrium? Zeroth Law of Thermodynamics First Law of Thermodynamics Second Law of Thermodynamics Third Law of Thermodynamics Which of the following is an example of an open system? A boiling beaker of water A sealed thermos flask A balloon filled with helium A copper wire carrying current Which of the following sets of properties contains only state functions? Internal energy, Enthalpy, Gibbs free energy Work, Heat, Internal energy Enthalpy, Heat, Pressure Volume, Work, Temperature A system is provided with 500 J of heat and it performs 200 J of work on the surroundings. What is the change in internal energy of the system? 300 J 700 J -300 J 200 J The work done during an isothermal reversible expansion of n moles of an ideal gas from V 1 to V 2 is given by: w = -nRT (V 2/V 1) w = -P V w = nRT (V 2/V 1) w = U - q Consider the following P-V diagram for an ideal gas. Path A is a straight line from (P 1, V 1) to (P 2, V 2) . Path B is a two-step process: isobaric then isochoric. Which is true regarding the internal energy change U ? U A = U B U A > U B U A < U B No relation can be established Assume each reaction is carried out in an open container. For which reaction will H = E ? H2(g) + Br2(g) -> 2HBr(g) C(s) + 2H2O(g) -> 2H2(g) + CO2(g) PCl5(g) -> PCl3(g) + Cl2(g) 2CO(g) + O2(g) -> 2CO2(g) The intensive property among the following is: Electromotive force ( E cell ) Internal Energy ( U ) Enthalpy ( H ) Gibbs Free Energy ( G ) Under isothermal condition, a gas at 300 K expands from 0.1 L to 0.25 L against a constant external pressure of 2 bar. The work done by the gas is (Given that 1 L bar = 100 J) 30 J -30 J 5 kJ 25 J Which one among the following is the correct option for right relationship between C P and C V for one mole of ideal gas? C P - C V = R C P = RC V C V = RC P C P + C V = R Match List I with List II. array ll List-I & List-II (Process) & (Conditions) A. Isothermal process & I. No heat exchange B. Isochoric process & II. Carried out at constant temperature C. Isobaric process & III. Carried out at constant volume D. Adiabatic process & IV. Carried out at constant pressure array Choose the correct answer from the options given below: A-IV, B-III, C-II, D-I A-IV, B-II, C-III, D-I A-I, B-II, C-III, D-IV A-II, B-III, C-IV, D-I The work done during reversible isothermal expansion of one mole of hydrogen gas at 25 C from pressure of 20 atmosphere to 10 atmosphere is (Given R = 2.0 cal K -1 mol -1 ) 0 calorie −413.14 calories 413.14 calories 100 calories At a certain temperature, T (K), during a process, 500 J is absorbed by the system and work of 200 J is done by the system. Then change in internal energy of the system is : 700 J 400 J 300 J 500 J An ideal gas expands isothermally from 10 -3 , m 3 to 10 -2 , m 3 at 300 , K against a constant pressure of 10 5 , N , m -2 . The work done on the gas is: -900 , J 900 , J 270 , J -2.303 , J A gas is allowed to expand in a well-insulated container against a constant external pressure of 2.5 , atm from an initial volume of 2.50 , L to a final volume of 4.50 , L . The change in internal energy U of the gas in joules will be: -505 , J +505 , J -1136.25 , J -500 , J The P-V diagram below shows two paths for an ideal gas to go from state A to state B. Which of the following is true? U 1 = U 2 and w 1 w 2 U 1 U 2 and w 1 = w 2 U 1 = U 2 and w 1 = w 2 U 1 U 2 and w 1 w 2 A system undergoes a cyclic process as shown in the P-V diagram. The net work done by the system in one cycle is: PV -PV Ï€PV Zero Identify the correct statement for an isothermal expansion of an ideal gas into vacuum: w = 0, q = 0, ΔU = 0 w eq 0, q = 0, ΔU = 0 w = 0, q eq 0, ΔU = 0 w = 0, q = 0, ΔU eq 0 Which law of thermodynamics introduced the concept of temperature? Zeroth Law First Law Second Law Third Law Calculate the work done (in L , atm ) when 2 , moles of an ideal gas expand isothermally and reversibly from 2 , L to 20 , L at 300 , K . -113.3 113.3 -49.2 -98.4 A gas expands adiabatically from V 1 to V 2 . The temperature of the gas will: Decrease Increase Remain the same First increase then decrease For which of the following reactions does H exactly equal U at all temperatures? H 2(g) + I 2(g) 2HI(g) PCl 5(g) PCl 3(g) + Cl 2(g) C(s) + O 2(g) CO 2(g) Both H 2(g) + I 2(g) 2HI(g) and C(s) + O 2(g) CO 2(g) The temperature of 2 , moles of an ideal gas is increased from 300 , K to 350 , K at constant pressure. The change in internal energy ( U ) is (given C v = 1.5R ): 150R 250R 100R 50R Consider the following P-V diagram for an ideal gas. Path A is isothermal and Path B is adiabatic expansion. Which statement is correct regarding work done ( |w| )? |w A| > |w B| |w B| > |w A| |w A| = |w B| Work done is zero for both The work done by an ideal gas in an open vessel during heating is: nR T Zero P V Isothermal work For an ideal gas, the value of the internal pressure, defined as ( U V ) T , is: Zero Positive Negative Depends on volume In a cyclic process, the graph of P versus V is a closed loop. If the cycle is clockwise, the net work done BY the system is: Positive Negative Zero Infinite During a free expansion of an ideal gas into a vacuum under adiabatic conditions, which of the following is true? q = 0, w = 0, U = 0 q = 0, w < 0, U > 0 q > 0, w = 0, U > 0 q = 0, w = 0, U > 0 For a real gas, the temperature at which the Joule-Thomson coefficient JT is zero is known as the: Inversion temperature Boyle temperature Critical temperature Consolute temperature What is the change in internal energy ( U ) when a system absorbs 15 , kJ of heat and performs 5 , kJ of work? 10 , kJ 20 , kJ -10 , kJ -20 , kJ The internal pressure ( U V ) T of an ideal gas is: 0 P RT/V a/V 2 The work done in a reversible adiabatic expansion of n moles of an ideal gas is: n C v (T 1 - T 2) n R T (V 2/V 1) P V n C p (T 2 - T 1) Calculate the work done (in kJ ) when 2 , moles of an ideal gas expand isothermally and reversibly from a volume of 10 , L to 100 , L at 300 , K . ( R = 8.314 , J , K -1 , mol -1 ) -11.48 , kJ -5.74 , kJ +11.48 , kJ -2.87 , kJ Consider the P-V diagram for an ideal gas. If the gas expands from V 1 to V 2 via two different paths: (A) Reversible isothermal and (B) Irreversible isothermal against a constant external pressure P ext = P 2 . Which statement is true regarding the work magnitude |w| ? |w A| > |w B| |w B| > |w A| |w A| = |w B| Work cannot be compared without T For an ideal gas, the work done in an isothermal expansion into vacuum (free expansion) is zero. What happens to the temperature of the gas? Temperature remains constant Temperature decreases Temperature increases Temperature first increases then decreases The correct option for free expansion of an ideal gas under adiabatic condition is q = 0, ΔT < 0 and w > 0 q < 0, ΔT = 0 and w = 0 q > 0, ΔT > 0 and w > 0 q = 0, ΔT = 0 and w = 0 Which of the following p-V curve represents maximum work done? When 1 mol of an ideal gas is compressed isothermally and reversibly from P 1 to P 2 , the work done is: 2.303 RT log P 2 P 1 2.303 RT log P 1 P 2 -RT ln P 2 P 1 RT ln P 2 P 1 For an ideal gas, the work done in a reversible adiabatic expansion from volume V 1 to V 2 is given by the expression: W = P 2V 2 - P 1V 1 - 1 W = nRT ( V 2 V 1 ) W = P V W = P 1V 1 - P 2V 2 - 1 Which of the following relationships is correct for an ideal gas? ( U / V) T = 0 ( U / P) T = 0 ( H / P) T = 0 All of these What is the sign of the work done ( w ) and the heat ( q ) for a gas undergoing an adiabatic compression? q = 0, w > 0 q = 0, w < 0 q > 0, w = 0 q < 0, w > 0 In a P-V diagram, an ideal gas is taken through a cycle A B C A , where A(1, 1) , B(4, 1) , and C(1, 4) (units in atm and L ). The net work done by the system in one cycle is: -4.5 , L atm 4.5 , L atm 9.0 , L atm -9.0 , L atm Which of the following is the criteria for spontaneity of a process at constant entropy ( S ) and constant volume ( V )? (dU) S,V < 0 (dG) T,P < 0 (dH) S,P < 0 (dA) T,V < 0 For an ideal gas, the internal pressure ( U V ) T is zero. This is because: There are no intermolecular forces of attraction or repulsion. The gas molecules are in constant random motion. The volume of the gas molecules is negligible compared to the total volume. The temperature of the gas is constant. Consider the reversible processes for 1.0 mol of an ideal gas as shown in the figure. w 1 , w 2 , w 3 and w 4 represent work done (in calories) in the processes 1, 2, 3 and 4, respectively; U 2 and U 4 are changes in the internal energy for the processes 2 and 4, respectively. [use R = 2 cal K -1 mol -1 ] The correct option is w 1 + w 3 = -2T 1 V 2 V 1 - 2T 2 V 4 V 3 w 2 + w 4 = U 2 - U 4 w 1 + w 2 = 2T 1 V 2 V 1 w 1 + w 2 + w 3 + w 4 = 0 In a Carnot cycle, the first step is: Isothermal expansion Adiabatic expansion Isothermal compression Adiabatic compression Which of the following conditions is correct for a free expansion of an ideal gas in an adiabatic process? q = 0, T = 0, w = 0 T < 0, w 0, q = 0 T = 0, w 0, q = 0 T > 0, w = 0, q = 0