Honors Chemistry: Introduction to Enthalpy, Kinetics, and Equilibrium

Comprehensive practice flashcards covering chemistry concepts including energy types, enthalpy stoichiometry, Hess' Law, Bond Energy, Entropy, Spontaneity (Gibbs Free Energy), Kinetics, and Equilibrium based on lecture notes and lab descriptions.

How is energy defined in the context of chemistry?

The ability to do work or produce heat.

What is the difference between potential and kinetic energy?

Potential energy is due to position or composition, while kinetic energy is due to the motion of an object.

What is the formula for kinetic energy provided in the notes?

$$KE = 1/2 mv$$

How is temperature defined relative to the motion of atoms or molecules?

It is a measure of the random motions of the atoms or molecules of a substance and is directly proportional to their kinetic energy.

What is the definition of heat energy ($q$)?

A flow of energy between two objects due to a temperature difference where thermal energy is transferred from a hot to a cold object.

What is the First Law of Thermodynamics?

The energy of the universe is constant; energy/heat cannot be created or destroyed.

Distinguish between a system and surroundings in thermodynamics.

The system is the part of the universe focused on (products/reactants), while surroundings are everything else (thermometer, atmosphere, beaker, etc.).

What are the characteristics of an exothermic reaction?

It has a negative sign because energy is released by the system to the surroundings.

What are the characteristics of an endothermic reaction?

It has a positive sign because energy is absorbed by the system from the surroundings.

In Lab 1, which chemicals produced an exothermic reaction, and how was this known?

Calcium chloride and vinegar; the thermometer (surroundings) measured an increase in temperature, meaning heat was released by the system.

What is thermal equilibrium?

The state where a substance achieves a constant temperature.

What is the definition of the heat of formation ($\Delta H_{rxn}$)?

The energy that accompanies the formation of one mole of a substance at Standard Temperature and Pressure (STP).

What is standard temperature for heat of formation calculations?

$$25^\circ C = 298\,K$$

What is the value of $\Delta H_{rxn}$ for elements in their natural states?

$$0\,kJ/mol$$

What is the basic formula for calculating heat energy ($q$)?

Heat energy ($q$) = specific heat ($c$) $\times$ mass of sample ($m$) $\times$ change in temperature ($\Delta T$).

What are the specific values for the heat of fusion and heat of vaporization in the notes?

$\Delta H_{fusion} = 6.02\,kJ/mol$ and $\Delta H_{vaporization} = 40.7\,kJ/mol$.

What is Hess' Law?

Adding the heat changes of reactions to get an overall net enthalpy ($kJ/mol$), where enthalpy remain constant whether in one or several steps.

What is bond energy?

The energy required to break a bond or the energy released when bonds are formed.

How is enthalpy calculated using bond energies?

$$\Delta H = \text{bonds broken (reactants)} - \text{bonds formed (products)}$$

How is entropy ($S$) defined?

A measure of disorder of moles in a substance; the tendency for molecules in the universe to become disordered.

What is the Second Law of Thermodynamics?

The entropy of the universe is always increasing.

Name four processes that increase entropy.

1. A solid dissolving into water; 2. Increase in temperature; 3. Phase change (solid to gas); 4. Increase in the number of moles of gas.

What is the quantitative formula for Gibbs' Free Energy ($G$)?

$$\text{Change in } G = \text{Change in } H - T \times (\text{Change in } S) / 1000$$

What indicates that a reaction is likely spontaneous?

A negative value for Change in $G$.

What is Activation Energy ($E_a$)?

The energy needed to start a reaction.

What is an activated complex?

A high energy, unstable transition state where reactant bonds are fully stretched and about to break.

How do catalysts affect activation energy?

They lower the activation energy required for reactants to become products, speeding up the reaction rate without being consumed.

What is chemical equilibrium?

The state where the rate of the forward reaction is equal to the rate of the reverse reaction, and concentrations remain constant.

According to LeChatelier’s Principle, how does a temperature increase affect an endothermic reaction?

Since heat acts as a reactant in an endothermic reaction, increasing temperature causes the reactants side to decrease and the products side to increase.

In Lab 3, what was the relationship between concentration and reaction time for the bisulfite and iodate ions?

The trial with the highest concentration took the least amount of time to react.