Distinguish Exothermic and Endothermic Reactions - Chemistry

1. Identify whether this process is exothermic or endothermic: freezing water releases heat to surroundings.

   Exothermic. Phase change releases energy.

2. Identify whether $q_{\text{system}}$ is $> 0$ or $< 0$ for an exothermic reaction.

   $q_{\text{system}} < 0$. System loses heat in exothermic reactions.

3. Which option describes an endothermic energy diagram: products at higher potential energy than reactants?

   Yes; products are higher than reactants. Energy increases from reactants to products.

4. Identify whether this process is exothermic or endothermic: deposition (gas to solid) releases heat.

   Exothermic. Gas-to-solid transition releases energy.

5. What is the definition of an endothermic reaction in terms of energy transfer?

   A reaction that absorbs energy (usually heat) from the surroundings. Energy absorption cools the surroundings.

6. Choose exothermic or endothermic: a beaker feels cold while a salt dissolves in water.

   Endothermic. Cold beaker indicates heat absorption.

7. Which sign of $\Delta H$ indicates an endothermic reaction: positive or negative?

   $\Delta H > 0$ (positive). Positive indicates energy absorbed by system.

8. Which sign of $\Delta H$ indicates an exothermic reaction: positive or negative?

   $\Delta H < 0$ (negative). Negative indicates energy released from system.

9. Identify whether this process is exothermic or endothermic: evaporation of water requires heat input.

   Endothermic. Liquid-to-gas transition needs energy.

10. Choose the correct type: an instant cold pack absorbs heat when chemicals mix.

    Endothermic. Heat absorption cools the surroundings.

11. What is the relationship between $q_{\text{system}}$ and $q_{\text{surroundings}}$ for heat exchange?

    $q_{\text{system}} = -q_{\text{surroundings}}$. Conservation of energy requires equal and opposite heat flows.

12. Which option is correct if products have lower enthalpy than reactants: exothermic or endothermic?

    Exothermic. Lower enthalpy means energy was released.

13. Which option describes the relative enthalpy: endothermic products lower or higher than reactants?

    Products have higher enthalpy than reactants. Energy is absorbed during the reaction.

14. Identify whether this process is exothermic or endothermic: melting ice absorbs heat from surroundings.

    Endothermic. Phase change requires energy input.

15. Identify exothermic or endothermic if heat is written as a reactant in the equation.

    Endothermic. Heat as reactant indicates absorption.

16. Which option describes the surroundings during an endothermic reaction: warmer or cooler?

    Cooler. Absorbed energy cools the surroundings.

17. Which option describes the reaction mixture temperature in an exothermic process: increases or decreases?

    Increases. Energy release heats the reaction mixture.

18. Which option describes the surroundings during an exothermic reaction: warmer or cooler?

    Warmer. Released energy heats the surroundings.

19. Identify whether $q_{\text{system}}$ is $ > 0 $ or $ < 0 $ for an exothermic reaction.

    $q_{\text{system}} < 0$. System loses heat in exothermic reactions.

20. Identify the type: acid-base neutralization typically releases heat in aqueous solution.

    Exothermic. Neutralization typically releases heat.

21. What is the definition of an exothermic reaction in terms of energy transfer?

    A reaction that releases energy (usually heat) to the surroundings. Energy release makes the surroundings warmer.

22. Which option is correct for endothermic: $q_{\text{system}}$ is positive or negative?

    $q_{\text{system}} > 0$. System absorbs heat in endothermic reactions.

23. Which option describes an exothermic energy diagram: products at lower potential energy than reactants?

    Yes; products are lower than reactants. Energy decreases from reactants to products.

24. Identify the type: thermal decomposition requires heating to break a compound into simpler substances.

    Endothermic. Breaking bonds requires energy input.

25. Identify whether this process is exothermic or endothermic: condensation of steam releases heat.

    Exothermic. Gas-to-liquid transition releases energy.

26. Which option describes bond energy changes: endothermic absorbs more energy breaking bonds than forming them?

    Yes; bond breaking absorbs more energy than bond formation releases. Net energy absorption occurs during endothermic reactions.

27. Identify exothermic or endothermic: the surroundings gain heat during the process.

    Exothermic. System releases heat to surroundings.

28. Which option is correct for endothermic: $H_{\text{products}} - H_{\text{reactants}}$ is positive or negative?

    Positive. Products have more enthalpy than reactants.

29. Identify exothermic or endothermic if $\Delta H = -125\ \text{kJ}$ for a reaction.

    Exothermic. Negative $\Delta H$ means exothermic.

30. Identify exothermic or endothermic if heat is written as a product in the equation.

    Exothermic. Heat as product indicates release.

31. Identify exothermic or endothermic: the temperature of the reaction mixture drops unless heated.

    Endothermic. Temperature drop indicates energy absorption.

32. What is the formula for reaction enthalpy in terms of enthalpies: $\Delta H = H_{\text{products}} - H_{\text{reactants}}$?

    $\Delta H = H_{\text{products}} - H_{\text{reactants}}$. Standard definition of enthalpy change.

33. Identify exothermic or endothermic if $\Delta H = +52\ \text{kJ}$ for a reaction.

    Endothermic. Positive $\Delta H$ means endothermic.

34. Which option describes the relative enthalpy: exothermic products lower or higher than reactants?

    Products have lower enthalpy than reactants. Energy is released during the reaction.

35. What does a positive value of $\Delta H$ mean about heat flow for the system?

    Heat flows into the system from the surroundings. System gains heat from surroundings.

36. Identify whether $q_{\text{system}}$ is $> 0$ or $< 0$ for an endothermic reaction.

    $q_{\text{system}} > 0$. System gains heat in endothermic reactions.

37. What does a negative value of $\Delta H$ mean about heat flow for the system?

    Heat flows out of the system to the surroundings. System loses heat to surroundings.

38. Which option describes the reaction mixture temperature in an endothermic process: increases or decreases?

    Decreases. Energy absorption cools the reaction mixture.

39. Identify whether this process is exothermic or endothermic: combustion of methane releases heat.

    Exothermic. Combustion releases heat energy.

40. Choose the correct type: a hand warmer packet produces heat when activated.

    Exothermic. Heat production is exothermic.

41. Choose exothermic or endothermic: dissolving $\text{CaCl}_2$ in water warms the solution.

    Exothermic. Warming effect indicates heat release.

42. Choose exothermic or endothermic: dissolving $\text{NH}_4\text{NO}_3$ in water cools the solution.

    Endothermic. Cooling effect indicates heat absorption.

43. Choose exothermic or endothermic: a reaction emits light and heat to the surroundings.

    Exothermic. Light and heat emission indicates energy release.

44. Which option is correct for exothermic: $H_{\text{products}} - H_{\text{reactants}}$ is positive or negative?

    Negative. Products have less enthalpy than reactants.

45. Identify whether this process is exothermic or endothermic: sublimation of dry ice requires energy.

    Endothermic. Solid-to-gas transition needs energy input.

46. What is the correct placement of heat in a thermochemical equation for an exothermic reaction?

    Heat is written on the product side. Heat appears as a product when released.

47. Which option is correct for exothermic: $q_{\text{system}}$ is positive or negative?

    $q_{\text{system}} < 0$. System releases heat in exothermic reactions.

48. Choose exothermic or endothermic: a reaction proceeds only while heat is continuously supplied.

    Endothermic. Continuous heating requirement indicates absorption.

49. Which option is correct if products have higher enthalpy than reactants: exothermic or endothermic?

    Endothermic. Higher enthalpy means energy was absorbed.

50. Identify exothermic or endothermic: the temperature of the reaction mixture rises without external heating.

    Exothermic. Temperature rise indicates energy release.

51. Identify exothermic or endothermic: cellular respiration releases energy from glucose oxidation.

    Exothermic. Glucose oxidation releases stored energy.

52. What is the correct placement of heat in a thermochemical equation for an endothermic reaction?

    Heat is written on the reactant side. Heat appears as a reactant when absorbed.

53. Identify exothermic or endothermic: photosynthesis requires energy input from sunlight.

    Endothermic. Light energy input drives the reaction.

54. Identify exothermic or endothermic: the surroundings lose heat during the process.

    Endothermic. Surroundings lose heat to the system.

55. Choose exothermic or endothermic: a beaker feels warm while a substance dissolves in water.

    Exothermic. Warm beaker indicates heat release.

56. Which option describes bond energy changes: exothermic releases more energy forming bonds than breaking them?

    Yes; bond formation releases more energy than bond breaking absorbs. Net energy release occurs during exothermic reactions.

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