General Chemistry Exam Study Guide: Thermodynamics, Gas Laws, and Chemical Reactions

Exam Topics Overview

This study guide summarizes the key topics and concepts for a General Chemistry exam, focusing on thermodynamics, gas laws, chemical reactions, and related calculations. Students should be familiar with definitions, equations, and applications for each topic listed below.

Oxidation-Reduction Reactions

Definitions and Identification

• Oxidation: The loss of electrons by a species.

• Reduction: The gain of electrons by a species.

• Oxidizing agent: The substance that causes oxidation (it is reduced).

• Reducing agent: The substance that causes reduction (it is oxidized).

• Be able to assign oxidation states to atoms in a reaction.

• Identify which species are oxidized and reduced in a reaction.

Example: In the reaction $2Na + Cl_2 \rightarrow 2NaCl$, sodium is oxidized and chlorine is reduced.

Gas Laws and Properties of Gases

Pressure and Its Measurement

• Pressure: Force exerted per unit area. Common units: atm, mmHg, Pa.

• Use barometer and manometer readings to determine pressure.

• Convert between pressure units.

Simple Gas Laws

• Boyle's Law: $P_1V_1 = P_2V_2$ (at constant T and n)

• Charles's Law: $\frac{V_1}{T_1} = \frac{V_2}{T_2}$ (at constant P and n)

• Avogadro's Law: $\frac{V_1}{n_1} = \frac{V_2}{n_2}$ (at constant P and T)

• Be able to identify and use the correct law for a given scenario.

The Ideal Gas Law

• Equation: $PV = nRT$

• Relates pressure (P), volume (V), amount of gas (n), temperature (T), and the gas constant (R).

• Use to calculate unknown variables and make predictions.

Standard Temperature and Pressure (STP)

• STP: 0°C (273.15 K) and 1 atm pressure.

• Molar volume at STP: 22.4 L for 1 mol of an ideal gas.

Mixtures of Gases and Partial Pressures

• Dalton's Law of Partial Pressures: $P_{total} = P_1 + P_2 + ... + P_n$

• Calculate mole fractions and partial pressures in mixtures.

Stoichiometry with Gases

• Apply stoichiometric relationships to gas reactions.

• Use the ideal gas law to relate moles of gas to volume.

Kinetic Molecular Theory

• Explains the behavior of gases in terms of particle motion.

• Relates temperature to average kinetic energy: $KE_{avg} = \frac{3}{2}RT$

Graham's Law of Effusion and Diffusion

• Graham's Law: $\frac{\text{Rate}_1}{\text{Rate}_2} = \sqrt{\frac{M_2}{M_1}}$

• Describes how lighter gases effuse and diffuse faster than heavier gases.

• Use to calculate molar mass of unknown gases.

Real Gases: Deviations from Ideal Behavior

• Real gases deviate from ideal behavior at high pressures and low temperatures.

• Van der Waals Equation: $\left(P + \frac{a n^2}{V^2}\right)(V - nb) = nRT$

• "a" corrects for intermolecular attractions; "b" corrects for finite molecular volume.

Thermodynamics

Definitions and Laws

• Thermodynamics: The study of energy and its transformations.

• First Law of Thermodynamics: Energy cannot be created or destroyed; it can only change forms.

• Law of Conservation of Energy: $\Delta E_{univ} = 0$

Internal Energy and State Functions

• Internal Energy (E): The total energy contained within a system.

• State functions depend only on the current state, not the path taken.

• Change in internal energy: $\Delta E = q + w$

• Sign conventions: $q$ (heat) and $w$ (work) are positive if energy flows into the system.

Heat, Work, and Calorimetry

• Heat capacity (C): Amount of heat required to raise the temperature of a substance by 1°C.

• Specific heat (c): Heat required to raise 1 g of a substance by 1°C.

• Calorimetry: Measurement of heat changes in chemical reactions.

• Equation: $q = mc\Delta T$

• Work for expansion/contraction: $w = -P\Delta V$

Constant Volume and Constant Pressure Calorimetry

• Bomb calorimeter: Measures $q_{v}$ (at constant volume).

• Coffee cup calorimeter: Measures $q_{p}$ (at constant pressure).

• Relationship: $q_{calorimeter} = \Delta E$ (constant volume), $q_{calorimeter} = \Delta H$ (constant pressure).

Enthalpy ($\Delta H$)

• Enthalpy: The heat content of a system at constant pressure.

• Equation: $\Delta H = \Delta E + P\Delta V$

• Endothermic reactions: $\Delta H > 0$ (heat absorbed).

• Exothermic reactions: $\Delta H < 0$ (heat released).

Thermochemical Equations and Hess's Law

• Thermochemical equations show enthalpy changes for chemical reactions.

• Hess's Law: The total enthalpy change for a reaction is the sum of the enthalpy changes for individual steps.

• Apply Hess's Law to calculate $\Delta H$ for complex reactions.

Standard Enthalpy of Formation ($\Delta H_f^\circ$)

• Enthalpy change for forming 1 mole of a compound from its elements in their standard states.

• Use tabulated values to calculate reaction enthalpy.

Key Tables

Comparison of Gas Laws

Law	Equation	Variables Held Constant
Boyle's Law	$P_1V_1 = P_2V_2$	n, T
Charles's Law	$\frac{V_1}{T_1} = \frac{V_2}{T_2}$	n, P
Avogadro's Law	$\frac{V_1}{n_1} = \frac{V_2}{n_2}$	P, T
Ideal Gas Law	$PV = nRT$	None

Types of Energy

Type	Description
Kinetic Energy	Energy of motion
Thermal Energy	Energy due to temperature
Chemical Energy	Energy stored in chemical bonds
Potential Energy	Energy due to position or composition

Additional Info

• Universal gas constant (R), bond enthalpies, and heat capacities will be provided on the exam.

• Students will be given a periodic table, equation sheet, and scratch paper for the exam.

• Non-programmable calculators are required; programmable/graphing calculators are not allowed.