Endothermic and Exothermic Problems

Consider the reaction:

H₂O (l) + energy → H₂ (g) + 1/2 O₂ (g)

Which phrase best describes this reaction?

• exothermic, releasing energy

• exothermic, absorbing energy

• endothermic, releasing energy

• endothermic, absorbing energy

When a substance was dissolved in water, the temperature of the water increased. This process is described as

• endothermic, with the release of energy

• endothermic, with the absorption of energy

• exothermic, with the release of energy

• exothermic, with the absorption of energy

Which potential energy diagram represents the reactions A + B → C + energy?

• 
• 
• 
• 

A solid is dissolved in a beaker of water. Which observation suggests that the process is endothermic?

• The solution gives off a gas.

• The solution changes color.

• The temperature of the solution decreases.

• The temperature of the solution increases.

Which phase change is exothermic?

• H₂O(s) → H₂O(l)

• H₂O(l) → H₂O(s)

• H₂O(s) → H₂O(g)

• H₂O(l) → H₂O(g)

When NH₄NO₃ is dissolved in water, the temperature of the water decreases. When NaOH is dissolved in a separate water sample, the temperature of the water increases. Based on these observations, it can be concluded that the dissolving of

• both salts is endothermic

• both salts is exothermic

• NH₄NO₃ is endothermic and the dissolving of NaOH is exothermic

• NH₄NO₃ is exothermic and the dissolving of NaOH is endothermic

Given the reaction: Fe + S → FeS + energy. Which statement about this reaction is true?

• It is endothermic

• It is exothermic

• The potential energy of the reactants is lower than the potential energy of the product.

• The potential energy of the reactants is the same as the potential energy of the product.

Given the reaction:

2H₂(g) + O₂(g) → 2H₂O(l) + 571.6kJ

What is the approximate ΔH for the formation of 1 mole of H₂O(l)?

• −285.8 kJ

• +285.8 kJ

• −71.6 kJ

• +571.6 kJ

The potential energy diagram shown represents the reaction

A + B → AB

Which statement correctly describes this reaction?

• It is endothermic and energy is absorbed.

• It is endothermic and energy is released.

• It is exothermic and energy is absorbed.

• It is exothermic and energy is released.

Which potential energy diagram represents an exothermic reaction?

• 
• 
• 
•