Thermochemistry exam

What is thermochemistry?

The study of heat and energy associated with chemical reactions and physical transformations.

What is enthalpy (H)?

A thermodynamic property of a system; the sum of the internal energy of a system plus the product of its pressure and volume: H = U + PV

Define an exothermic reaction.

A reaction that releases heat to the surroundings; [Delta]H < 0

Define an endothermic reaction.

A reaction that absorbs heat from the surroundings; [Delta]H > 0

What is thermochemistry?

The study of heat and energy associated with chemical reactions and physical transformations.

What is enthalpy (H)?

A thermodynamic property of a system; the sum of the internal energy of a system plus the product of its pressure and volume: H = U + PV

Define an exothermic reaction.

A reaction that releases heat to the surroundings; [Delta]H < 0

Define an endothermic reaction.

A reaction that absorbs heat from the surroundings; [Delta]H > 0

Define standard enthalpy of formation (\Delta H_f^o).

The enthalpy change when one mole of a substance is formed from its elements in their standard states (usually at 298 K and 1 atm).

How do you calculate the enthalpy change of a reaction using standard enthalpies of formation?

\Delta H{rxn}^o = \Sigma n \Delta Hf^o(products) - \Sigma n \Delta H_f^o(reactants), where n is the stoichiometric coefficient.

What is bond enthalpy?

The enthalpy change required to break one mole of a particular bond in the gaseous phase.

How can bond enthalpies be used to estimate the enthalpy change of a reaction?

\Delta H \approx \Sigma Bond\, enthalpies\,(bonds\, broken) - \Sigma Bond\, enthalpies\,(bonds\, formed)

Define heat capacity (C).

The amount of heat required to raise the temperature of a substance by one degree Celsius (or one Kelvin).

Define specific heat capacity (c).

The amount of heat required to raise the temperature of one gram of a substance by one degree Celsius (or one Kelvin).

What is calorimetry?

The process of measuring the amount of heat released or absorbed during a chemical or physical change.

What is the equation for heat transfer (q) in calorimetry?

q = mc\Delta T, where m is mass, c is specific heat capacity, and [Delta]T is the change in temperature.

What is chemical equilibrium?

A state in which the rates of forward and reverse reactions are equal, and the net change in concentrations of reactants and products is zero.

Define the equilibrium constant (K).

The equilibrium constant (K) is the ratio of products to reactants at equilibrium, each raised to the power of their stoichiometric coefficients.

What is the reaction quotient (Q)?

The reaction quotient (Q) is a measure of the relative amount of products and reactants present in a reaction at any given time.

If Q < K, the reaction will proceed forward to form more products. If