Podcast
Questions and Answers
Explain how the enthalpy change (ΔH) indicates whether a reaction is exothermic or endothermic.
Explain how the enthalpy change (ΔH) indicates whether a reaction is exothermic or endothermic.
A negative ΔH indicates an exothermic reaction because the products have less energy than the reactants, releasing heat. A positive ΔH indicates an endothermic reaction because the products have more energy than the reactants, absorbing heat.
Describe what happens to the temperature of the surroundings during an exothermic reaction and why this temperature change occurs.
Describe what happens to the temperature of the surroundings during an exothermic reaction and why this temperature change occurs.
The temperature of the surroundings increases. This is because the reaction releases heat into the surroundings, increasing the kinetic energy of the surrounding molecules.
Explain why it is not possible to directly measure enthalpy (H), but enthalpy change (ΔH) can be easily measured.
Explain why it is not possible to directly measure enthalpy (H), but enthalpy change (ΔH) can be easily measured.
Enthalpy (H) is a state function that represents the total heat content of a system, which is difficult to quantify absolutely. Instead, we measure the change in heat content during a reaction, which is the enthalpy change (ΔH).
Provide an example, other than those listed, of an everyday process that represents an endothermic reaction, and explain why it is endothermic.
Provide an example, other than those listed, of an everyday process that represents an endothermic reaction, and explain why it is endothermic.
Explain the difference in energy levels between the reactants and products in an exothermic reaction using the terms 'Hproducts' and 'Hreactants'.
Explain the difference in energy levels between the reactants and products in an exothermic reaction using the terms 'Hproducts' and 'Hreactants'.
For an endothermic reaction, describe how the enthalpy change (ΔH) is related to the energy absorbed from the surroundings.
For an endothermic reaction, describe how the enthalpy change (ΔH) is related to the energy absorbed from the surroundings.
Why do hand warmers get hot?
Why do hand warmers get hot?
Describe what happens to the temperature of the surroundings during an endothermic reaction and explain why this temperature change occurs.
Describe what happens to the temperature of the surroundings during an endothermic reaction and explain why this temperature change occurs.
Predict whether the change in enthalpy, $\Delta H$, for the reaction of an acid reacting with a metal would be positive or negative. Explain your answer.
Predict whether the change in enthalpy, $\Delta H$, for the reaction of an acid reacting with a metal would be positive or negative. Explain your answer.
Are thermal decomposition reactions exothermic or endothermic? Explain your answer.
Are thermal decomposition reactions exothermic or endothermic? Explain your answer.
Flashcards
Exothermic Reaction
Exothermic Reaction
Reactions that release energy, causing an increase in temperature of the surroundings.
Endothermic Reaction
Endothermic Reaction
Reactions that absorb energy from the surroundings, usually in the form of heat.
Enthalpy (H)
Enthalpy (H)
The total energy content of a system held at constant pressure.
Enthalpy Change (ΔH)
Enthalpy Change (ΔH)
Signup and view all the flashcards
ΔH in Exothermic Reactions
ΔH in Exothermic Reactions
Signup and view all the flashcards
ΔH in Endothermic Reactions
ΔH in Endothermic Reactions
Signup and view all the flashcards
Study Notes
- Chemical reactions often involve energy transfer with the surroundings.
- Energy release in a reaction leads to a temperature increase in the reaction mixture and its immediate environment.
- Reactions that release energy are classified as exothermic.
Exothermic Reactions
- Acids reacting with metals exemplify exothermic reactions.
- Oxidation of iron, as utilized in hand warmers, is an exothermic process.
- The thermite reaction, involving aluminium and iron(III) oxide, is exothermic.
Endothermic Reactions
- Energy absorption from the surroundings occurs as heat in endothermic reactions.
- Melting ice is an endothermic process requiring energy input.
- Dissolving ammonium chloride in water, such as in cold packs, is endothermic.
- Thermal decomposition of group 2 carbonates needs energy input, making it endothermic.
- The amount of heat transferred in a chemical reaction depends on the conditions under which it occurs.
- Most lab reactions happen under constant pressure.
- Enthalpy (H) is the total energy content of a system at constant pressure.
- Enthalpy cannot be directly measured.
- Enthalpy change (ΔH) can be easily measured in joules (J) or kilojoules (kJ).
- ΔH is calculated as H(products) − H(reactants).
- In exothermic reactions, heat is released so H(products) < H(reactants), meaning ΔH is negative.
- In endothermic reactions, heat is absorbed so H(products) > H(reactants), meaning ΔH is positive.
- Enthalpy changes are represented using enthalpy profile diagrams.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
