NET, IAS, State-SET (KSET, WBSET, MPSET, etc.), GATE, CUET, Olympiads etc.: Chemistry MCQs (Practice_Test 2 of 31)
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- For a process at 451 K and constant pressure, Ssurr is-326 J K − 1. Calculate the quantity of heat (in kJ) absorbed by the system.
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- Which of the following produces an INCREASE in entropy of the system?
- H2O (l) ⇾ H2O (s)
- 2O2 (g) + 2SO (g) ⇾ 2SO3 (g)
- 2CH3OH (g) + 3O2 (g) ⇾ 2CO2 (g) + 4H2O (l)
- I2 (s) ⇾ I2 (l)
- None of the above:
- The gas-phase reaction between H2 and Cl2 can be initiated by ultraviolet light at 25oC, H2 (g) + Cl2 (g) ⇾ 2HCl (g)
- Using the thermodynamic data provided below, calculate the standard free energy change (in kJ) at 25oC for this reaction.Compound Hfo, kJ mol-1So, J mol-1 K − 1, H20130.57, Cl20222.96, HCl-92.307186. 80 4.In lecture, you observed the following reaction, 2H2 (g) + O2 (g) ⇾ 2H2O (g) For this reaction, Ho =-241.8 kJ and So =-88.8 J K − 1. Assuming that Ho = H and So = S at all temperatures, calculate the temperature (in K) at which this reaction would become non-spontaneous.
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- For a particular chemical reaction at 400oC, G =-67 kJ. Calculate the time (in seconds) it will take for the reaction to reach completion.
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- For a particular chemical reaction, Ho is positive and So is negative. Which of the following statements about the spontaneity of the reaction under standard conditions is TRUE?
- The reaction will be spontaneous only if the magnitude of Ho is large enough to overcome the unfavorable entropy change.
- The reaction will be spontaneous only if the magnitude of So is large enough to overcome the unfavorable enthalpy change.
- The reaction will be spontaneous regardless of the magnitudes of Ho and So.
- The reaction cannot be spontaneous.
- The reaction will be spontaneous only of Go is positive.
- Which of the following is TRUE for an operating voltaic cell?
- G > 0; E = 0
- G < 0; E < 0
- G = 0; E > 0
- G = 0; E = 0
- G < 0; E > 0
- Which of the following produces a DECREASE in entropy of the system? Hint: The system is shown in bold.
- Dissolving sugar in a cup of coffee.
- Condensation of water on the surface of a glass of iced tea on a hot summer day.
- Boiling water in a pot on the stove to make spaghetti.
- Allowing the liquid propane in a gas grill to escape from the tank.
- Producing CO2 gas from baking soda (NaHCO3) when baking a cake.
- Consider the following reaction and thermodynamic data, 2H2O2 (aq) ⟺ 2H2O (l) + O2 (g) substance Hfo, kJ mol-1So, J mol-1 K − 1, H2O2 (aq) -191.17143. 9, H2O (l) -285.8369. 91, O2 (g) 0205.14, Calculate the value (in kJ) of Go at 25oC.
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- For a particular chemical reaction, both Ho and So are negative. Which of the following statements about the spontaneity of the reaction under standard conditions is TRUE?
- The reaction will be spontaneous only if the magnitude of Ho is large enough to overcome the unfavorable entropy change.
- The reaction will be spontaneous only if the magnitude of So is large enough to overcome the unfavorable enthalpy change.
- The reaction will be spontaneous regardless of the magnitudes of Ho and So.
- The reaction cannot be spontaneous.
- The reaction will be spontaneous only of Go is positive.
- The boiling point of a substance is the temperature at which equilibrium is established between the liquid and the vapor. CH3CH2OH (l) ⟺ CH3CH2OH (g) Calculate the boiling point (in K) of ethanol, CH3CH2OH, if H = 42.6 kJ and S = 122 J⟋K for this process.
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- What is the significance of the Third Law of Thermodynamics? Choose the best answer.
- The absolute entropy of a substance decreases with increasing temperature.
- The change in entropy of the universe must be positive for a spontaneous process.
- The absolute value of entropy can be measured for some very pure substances.
- The change in entropy of the universe equals the sum of the change in entropy of the system plus the change in entropy of the surroundings.
- The entropy of the universe is constant.
- The Ksp for the sparingly soluble salt barium chromate (BaCrO4) at 25oC is equal to 2.0 × 10 − 10. Calculate Go (in kJ) for the following reaction. BaCrO4 (s) ⟺ Ba2 + (aq) + CrO42- (aq)
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- Chemistry 116 student determined the value of Ksp for a saturated solution of borax at several different temperatures. The value for Sofor the dissolution of borax in water can be determined from:
- the slope of the line resulting from a plot of ln Ksp versus (1⟋T)
- the y-intercept of the line resulting from a plot of ln Ksp versus T
- the slope of the line resulting from a plot of Ksp versus (1⟋T)
- the y-intercept of the line resulting from a plot of ln Ksp versus (1⟋T)
- the slope of the curve at 25oC from a plot of ln Ksp versus T
- Consider the following gas-phase reaction, 2NO2 (g) ⟺ 2NO (g) + O2 (g) , Go =+ 70.5 kJ, If 1.00 mole of NO2 (g) is placed in a 1.00 − L flask (no NO (g) or O2 (g) initially) at 25oC, which of the following statements is TRUE?
- The reaction will occur spontaneously from left to right.
- The reaction will occur spontaneously from right to left.
- The reaction is not spontaneous in either direction.
- The reaction is spontaneous in both directions.
- At equilibrium, the concentrations of NO (g) and O2 (g) will be much larger than the concentration of NO2 (g) .