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Endothermic and exothermic processes

Chemistry • Energy & Heat in Chemical Processes • Knowledge-Based • 5 questions

Endothermic and exothermic processes Knowledge-Based Download PDF

Chemistry · Thermochemistry & Thermodynamics · Chemistry · Energy & Heat in Chemical Processes

5 Chemistry practice questions on Endothermic and exothermic processes. Questions that assess core concepts and understanding.

Questions

  1. 1.

    Which of the following thermochemical equations represents an endothermic reaction?

    • A) CH4(g)+2O2(g)→CO2(g)+2H2O(l)+891 kJ\text{CH}_4(g) + 2\text{O}_2(g) \rightarrow \text{CO}_2(g) + 2\text{H}_2\text{O}(l) + 891\text{ kJ}
    • B) CaCO3(s)+178 kJ→CaO(s)+CO2(g)\text{CaCO}_3(s) + 178\text{ kJ} \rightarrow \text{CaO}(s) + \text{CO}_2(g)
    • C) 2H2(g)+O2(g)→2H2O(l)+572 kJ2\text{H}_2(g) + \text{O}_2(g) \rightarrow 2\text{H}_2\text{O}(l) + 572\text{ kJ}
    • D) N2(g)+3H2(g)→2NH3(g)+92 kJ\text{N}_2(g) + 3\text{H}_2(g) \rightarrow 2\text{NH}_3(g) + 92\text{ kJ}
  2. 2.

    Which of the following physical phase transitions represents an exothermic process?

    • A) Melting of solid ice into liquid water
    • B) Vaporization of liquid acetone into gaseous acetone
    • C) Sublimation of solid dry ice into carbon dioxide gas
    • D) Condensation of water vapor into liquid water
  3. 3.

    A chemical reaction occurs in which the total enthalpy of the products is greater than the total enthalpy of the reactants. Which statement correctly classifies this process and specifies the sign of the enthalpy change (ΔH\Delta H)?

    • A) It is an exothermic process, and ΔH<0\Delta H < 0.
    • B) It is an endothermic process, and ΔH>0\Delta H > 0.
    • C) It is an endothermic process, and ΔH<0\Delta H < 0.
    • D) It is an exothermic process, and ΔH>0\Delta H > 0.
  4. 4.

    In an exothermic chemical reaction, how do the energy required to break bonds in the reactants and the energy released upon forming bonds in the products compare?

    • A) More energy is absorbed to break reactant bonds than is released when product bonds form, resulting in a positive enthalpy change.
    • B) Less energy is absorbed to break reactant bonds than is released when product bonds form, resulting in a negative enthalpy change.
    • C) Energy is absorbed only during product bond formation, whereas breaking reactant bonds always releases energy to the surroundings.
    • D) The energy absorbed to break reactant bonds equals the energy released during product bond formation, resulting in zero net heat exchange.
  5. 5.

    Which statement correctly describes the thermal energy exchange and the observed temperature change during an endothermic chemical reaction taking place in an aqueous solution?

    • A) Heat is released by the reacting system into the solvent, causing the measured temperature of the solution to increase.
    • B) Thermal energy is absorbed by the reacting system from the solvent, causing the measured temperature of the solution to decrease.
    • C) The enthalpy change of the process is negative, leading to a net transfer of thermal energy from the system to the surroundings.
    • D) Chemical bonds in the products store less potential energy than those in the reactants, resulting in a warming of the surrounding water.