Endothermic and Exothermic Reactions Flashcards
(16 cards)
Q: What is heat?
A: Heat is a form of energy transferred due to a temperature difference.
Q: What does temperature measure?
A: Temperature measures the average kinetic energy of particles.
Q: What is an exothermic reaction?
A: A reaction that releases heat to the surroundings; ΔH is negative.
Q: What is an endothermic reaction?
A: A reaction that absorbs heat from the surroundings; ΔH is positive.
Q: How do these reactions relate to the law of conservation of energy?
A: Energy is not lost or created—just transferred between system and surroundings.
Q: How does bond breaking/forming relate to energy?
A: Breaking bonds absorbs energy (endothermic); forming bonds releases energy (exothermic).
Q: What does an exothermic enthalpy diagram show?
A: Products are lower in energy than reactants; energy released.
Q: What does an endothermic enthalpy diagram show?
A: Products are higher in energy than reactants; energy absorbed.
Q: How does enthalpy change (ΔH) indicate stability?
A: A negative ΔH suggests products are more stable; a positive ΔH suggests reactants are more stable.
Q: Why is a reaction exothermic or endothermic in terms of bond enthalpies?
A: If more energy is released in forming bonds than used to break them, it’s exothermic (vice versa for endothermic).
Q: What’s the sign of ΔH in exothermic vs endothermic reactions?
A: Exothermic: ΔH < 0; Endothermic: ΔH > 0
Q: What are the limitations of using average bond enthalpies?
A: They are average values and don’t account for specific molecular environments.
Q: What is the formula to calculate heat change (Q)?
𝑄=𝑚𝑐Δ𝑇
Where:
m = mass (g)
c = specific heat capacity (J/g°C)
ΔT = temperature change (°C)
Q: How to calculate enthalpy change (ΔH) for a reaction in solution?
Use:
𝑄=𝑚𝑐Δ𝑇
Convert Q to kJ
Divide by moles of limiting reactant to find ΔH (kJ/mol)
Q: What data is needed to analyse heat of combustion/neutralisation?
A: Mass, specific heat capacity, temperature change, and number of moles.
Q: What kind of reaction is neutralisation usually?
A: Exothermic.
