Enthalpy

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What is Enthalpy?

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Enthalpy (H) is a thermodynamic quantity that represents the total heat content of a system. It is used to measure the energy changes during chemical reactions.

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What does ΔH represent in a chemical reaction?

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ΔH represents the change in enthalpy during a chemical reaction, indicating whether the reaction absorbs or releases heat.

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What is an exothermic reaction?

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An exothermic reaction is a chemical reaction that releases heat to its surroundings, resulting in a negative ΔH value.

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What is an endothermic reaction?

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An endothermic reaction is a chemical reaction that absorbs heat from its surroundings, resulting in a positive ΔH value.

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How do you calculate ΔH for a reaction?

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ΔH can be calculated using the formula: ΔH = H(products) - H(reactants).

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What is the significance of a negative ΔH value?

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A negative ΔH value indicates that the reaction is exothermic, meaning it releases energy.

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What is the significance of a positive ΔH value?

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A positive ΔH value indicates that the reaction is endothermic, meaning it absorbs energy.

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In the reaction C + O2 → CO2 + 60 kJ, what is ΔH?

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ΔH = -60 kJ, indicating an exothermic reaction.

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In the reaction N2 + O2 → 2NO with ΔH = 180 kJ, how is it represented?

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N2 + O2 + 180 kJ → 2NO, indicating that energy is absorbed.

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What is the enthalpy change for the reaction HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l) with ΔH°298 = -58 kJ/mol?

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The reaction is exothermic, releasing 58 kJ of energy.