NET, IAS, State-SET (KSET, WBSET, MPSET, etc.), GATE, CUET, Olympiads etc.: Chemistry MCQs (Practice_Test 4 of 31)
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- For mercury the molar entropy of vaporization is 92.92 J K − 1 mol-1 and the molar enthalpy of vaporization is 58.51 kJ mol-1. Therefore, the normal boiling point of mercury in oC is:
- 273oC
- 357oC
- 516oC
- 670oC
- unable to determine unless G of vaporization is known.
- Which statement is TRUE for an operating electrolytic cell?
- G > 0 and Ecell < 0
- G = 0 and Ecell > 0
- G < 0 and Ecell = 0
- G = 0 and Ecell = 0
- G > 0 and Ecell > 0
- For which ONE of the following reactions does the entropy of the system DECREASE?
- NH4NO3 (s) ⇾ NH4 + (aq) + NO3- (aq)
- 2 H2O2 (l) ⇾ 2 H2O (l) + O2 (g)
- Ba (OH) 2.8H2O (s) + 2 NH4SCN (s) ⇾ Ba (SCN) 2 (aq) + 2 NH3 (aq) + 10 H2O (l)
- NO (g) + NO2 (g) ⇾ N2O3 (g)
- CO2 (s) ⇾ CO2 (g)
- For a particular chemical reaction at 25oC, H =-432 kJ. Which of the following statements is TRUE?
- The reaction will be spontaneous, at any temperature, if S is positive.
- The reaction will be spontaneous, at any temperature, if S is negative.
- The reaction will be spontaneous only if G is positive.
- The reaction can never be spontaneous, at any temperature.
- There is insufficient information provided to answer this question.
- For a particular chemical reaction, Ho =+ 60.0 kJ and So =+ 121 J⟋K. At what temperature (in K) would this reaction become spontaneous?
- Consider the gas-phase hydrogenation of ethylene, C2H2, to produce ethane, C2H6, C2H2 (g) + 2 H2 (g) ⇾ C2H6 (g) and the following thermodynamic data: Substance Hfo, kJ mol-1So, J mol-1 K − 1 C2H2 (g) 227.0201. 0 H2 (g) 0131.0 C2H6 (g) -84.70229. 5 Under standard conditions, which of the following statements is TRUE?
- The reaction is spontaneous; Ho is favorable while So is not.
- The reaction is spontaneous; So is favorable while Ho is not.
- The reaction is not spontaneous; So is favorable while Ho is not.
- The reaction is not spontaneous; Ho is favorable while So is not.
- The reaction is not spontaneous; neither Ho nor So are favorable.
- Consider the gas-phase reaction of hydrogen, H2, and oxygen, O2, to produce water, 2 H2 (g) + O2 (g) ⇾ 2 H2O (g) and the following thermodynamic data: Substance Gfo, kJ⟋mol H2 (g) 0 O2 (g) 0 H2O (g) -228.6 Calculate the value of the equilibrium constant for this reaction under standard conditions.
- Consider the gas-phase reaction of hydrogen, H2, with carbon monoxide, CO, to form formaldehyde, H2CO, in a closed system at constant pressure, H2 (g) + CO (g) ⇾ H2CO (g) and the following thermodynamic data, substance Hfo, kJ mol-1So, J mol-1 K − 1, H2 (g) 0131, CO (g) -110198, H2CO (g) -116219 If the initial concentration of CO (g) is 1.5 M and the initial concentration of H2 (g) is 2.3 M, calculate the concentration (in M) of H2CO (g) at equilibrium, at 298 K.
- N⟋A
- N⟋A
- N⟋A
- N⟋A
- For a certain process, S (system) > 0 and S (surroundings) > 0. The process:
- is spontaneous.
- is exothermic.
- decreases the entropy of the universe.
- is endothermic.
- is at equilibrium.
- In which case does the spontaneity of a reaction depend on the temperature?
- H = 0 and S < 0
- H > 0 and S > 0
- H < 0 and S = 0
- H > 0 and S = 0
- H < 0 and S > 0
- Consider the following reaction: H2O (g) + Cl2O (g) ⟺ 2 HOCl (g) For this reaction, Keq = 0.090 at 25oC. Calculate the value (in kJ⟋mol) of Go for this reaction.
- For a particular process at 500 K, G =-3.0 kJ and H =-23.0 kJ. If the process is carried out reversibly, caluclate the amount (in kJ) of useful work that can be performed.
- N⟋A
- N⟋A
- N⟋A
- N⟋A
- Which of the following statements concerning the change in Go and G during a chemical reaction is most correct?
- Go remains constant while G changes and becomes equal to Go at equilibrium.
- Both Go and G remain constant during a chemical reaction.
- Initially both G and Go are equal to zero. The value of Go changes to a value determined by the equilibrium constant; the value of G peaks and then decreases to zero at equilibrium.
- Go remains constant if the reaction is carried out under standard conditions; G remains constant if the reaction is carried out under non-standard conditions.
- Go remains constant while G changes and becomes equal to zero at equilibrium.
- The enthalpy of vaporization of ethanol is 38.7 kJ⟋mol at its boiling point of 78oC. Calculate the change in entropy (in J⟋mol) of the surroundings when 1.00 mole of ethanol is vaporized at 78oC and 1.00 atm of pressure.
- N⟋A
- N⟋A
- N⟋A
- N⟋A
- A certain chemical reaction carried out at constant temperature and pressure has S > 0. What can you conclude about the spontaneity of this reaction?
- The reaction is not spontaneous if it is endothermic and the temperature is sufficiently high.
- The reaction is not spontaneous at any temperature.
- The reaction is not spontaneous if it is exothermic and the temperature is sufficiently low.
- The reaction is only spontaneous at high temperatures.
- The reaction is spontaneous if it is exothermic and the temperature is sufficiently high.
- Consider the following reaction: 2 C (graphite) + H2 (g) ⇾ C2H2 (g) Go = 209.2 kJ at 25oC, P (H2) = 100 atm, P (C2H2) = 0.10 atm Calculate the value (in kJ) of G for this reaction.
- N⟋A
- N⟋A
- N⟋A
- N⟋A
- We observed that when two white crystalline substances were mixed the beaker froze to the wooden board it was sitting on. The reaction is as follows: Ba (OH) 2: 8H2O (s) + 2 NH4NO3 (s) ⇾ Ba (NO3) 2 (aq) + 2 NH3 (g) + 10 H2O (l) For this reaction, Ho = 170.44 kJ and So = 657.4 J⟋K. Which of the following statements must be TRUE about the process?
- Enthalpy is favorable and entropy is unfavorable.
- Neither entropy nor entropy are favorable.
- Both enthalpy and entropy are favorable.
- Enthalpy is unfavorable and entropy is favorable.
- The process is not spontaneous because it had to be stirred.