# Enthalpy Quiz

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## 1. When 1.0 mole of ZnO(s) decomposes, the ΔH = 348 kJ/mol of heat energy. What does this tell you about the formation of ZnO(s)?

• The formation of ZnO(s) is exothermic.
• The formation of ZnO(s) is endothermic.
• The formation of ZnO(s) does not require energy.
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## 2. Under what set of standard conditions do standard enthalpies occur?

• A stated temperature of 297 K (24°C), a pressure of 100 kPa (2 atmosphere) and a concentration of 2.0 mol dm−3 (for reactions with aqueous solutions).
• A stated temperature of 298 K (25°C), a pressure of 100 kPa (1 atmosphere) and a concentration of 1.0 mol dm−3 (for reactions with aqueous solutions).
• A stated temperature of 297 K (24°C), a pressure of 100 kPa (1 atmosphere) and a concentration of 1.0 mol dm−3 (for reactions with aqueous solutions).
• A stated temperature of 298 K (25°C), a pressure of 100 kPa (1 atmosphere) and a concentration of 2.0 mol dm−3 (for reactions with aqueous solutions).

## 3. What does Hess' Law state?

• If a reaction can take place by more than one route and the initial and final conditions are the same, the total enthalpy change is the same for each route.
• When a system in dynamic equilibrium is subjected to a change, the point of equilibrium will shift to minimise the change.
• No materials are being added or taken away from a system in equilibrium, and no external conditions, such as temperature or pressure, are altered.

## 4. What is enthalpy change of formation?

• The enthalpy change that takes accompanies a rection in the molar quantities expressed in a chemical equation under standard conditions.
• Tthe enthalpy change when solutions of an acid and an alkali react together under standard conditions to produce 1 mole of water.
• The enthalpy change of a compound when one mole of the compound, in its standard state, is formed from its constituent elements in their standard states.
• The enthalpy change that takes place when one mole a substance reacts completly with oxygen under standard conditions.

## 5. The difference in the heat contents of the products and the reactants is called...?

• Heat of the reaction
• Temperature
• Heat of calorimetry