Enthalpy Change Quiz

What is enthalpy change (ΔH)?

• The change in pressure during a reaction

• The change in temperature of a substance

• The heat absorbed or released during a chemical reaction at constant pressure

• The amount of work done by the system

If a chemical reaction has a negative enthalpy change (ΔH < 0), the reaction is:

• Endothermic

• Exothermic

• Isothermal

• Equilibrium

In an endothermic reaction, the system:

• Releases heat to the surroundings

• Absorbs heat from the surroundings

• Maintains constant temperature

• Does not exchange energy with the surroundings

Which of the following has the correct sign of ΔH for the combustion of a fuel?

• ΔH = 0

• ΔH > 0

• ΔH < 0

• ΔH is undefined

The standard enthalpy change of formation (ΔH°f) refers to:

• The enthalpy change when one mole of a compound is formed from its elements in their standard states

• The enthalpy change when a substance melts

• The enthalpy change of a neutralization reaction

• The enthalpy change of a gas expanding

What is the standard condition for measuring standard enthalpy changes (ΔH°)?

• 0°C and 1 atm

• 25°C and 1 atm

• 100°C and 1 atm

• 25°C and 100 atm

Which of the following processes involves a positive enthalpy change (ΔH > 0)?

• Combustion

• Freezing

• Condensation

• Evaporation

Hess’s Law states that:

• ΔH depends on the temperature of the system

• The total enthalpy change is independent of the route taken

• The enthalpy change is always negative

• Pressure has no effect on enthalpy change

Which of the following statements is true about exothermic reactions?

• Products have more enthalpy than reactants

• Heat is absorbed from the surroundings

• ΔH is negative

• There is no energy change

What instrument is commonly used to measure enthalpy change in a laboratory?

• Barometer

• Calorimeter

• Thermocouple

• Manometer