AP Chemistry Thermochemistry

Front

What is thermochemistry?

Back

Thermochemistry is the study of the heat energy associated with chemical reactions and changes of state.

Front

Define endothermic reaction.

Back

An endothermic reaction is a chemical reaction that absorbs heat from its surroundings, resulting in a decrease in temperature of the surroundings.

Front

In an endothermic reaction, do reactants have a higher or lower energy than the products?

Back

Reactants have lower energy than the products.

Front

What is bond enthalpy?

Back

Bond enthalpy is the amount of energy required to break one mole of a bond in a gaseous substance.

Front

Calculate the enthalpy change for the decomposition of hydrogen chloride: 2 HCl -> H2 + Cl2 using average bond enthalpies.

Back

The enthalpy change is +184 kJ.

Front

What is the enthalpy of formation?

Back

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

Front

Using the enthalpies of formation, how do you calculate the enthalpy change for a reaction?

Back

Subtract the total enthalpy of the products from the total enthalpy of the reactants.

Front

What is the enthalpy change for the reaction Ca(OH)2 -> CaO + H2O given the enthalpies of formation?

Back

The enthalpy change is 62.8 kJ.

Front

How much energy is required to convert 1 mole of liquid water to gaseous water?

Back

44.0 kJ.

Front

If 6,000 Joules of energy is added to two blocks of aluminum (1 kg and 10 kg), which will have the smallest change in temperature?

Back

The 10 kg block will have the smallest change in temperature.