# AP® Chemistry Formula Sheet and Periodic Table

AP® Chemistry is a course that covers a lot of information, including the meaning and function of several equations, constants, and the periodic table. This may seem like an overwhelming amount of content, but you can relax because you do not have to memorize it all!

## What is the AP Chemistry Formula Sheet?

The AP Chemistry formula sheet is two pages long and contains unit abbreviations as well as equations, constants, and definitions of variables grouped together by topic. An AP Chemistry formula sheet and the periodic table are provided at the beginning of both the multiple-choice and free-response sections of the AP Chemistry exam.

While you may not have to memorize all of the information given to you on the AP Chemistry equation sheet and periodic table, you still need to understand the formulas and variables it contains, know how to apply the equations, and understand the meaning of the values on the periodic table. Printing out a copy of the AP Chemistry periodic table and AP Chemistry formula sheet to use while you take practice tests is great preparation for exam day.

### Using the AP Chemistry Formula Sheet

To make your exam prep easier and faster, we have compiled a copy of the AP Chemistry Formula Sheet that is usually included in your AP Chemistry exam booklet. Use this sheet as you work through questions in your AP Chemistry practice exams and become familiar with the layout of the AP Chemistry equations and constants. Doing this will help you access these formulas quickly when solving a problem. This will significantly improve your speed of answering a question on exam day.

Below is everything you need to know about what information is provided on the AP Chemistry equation sheet and periodic table.

### Units at First Glance

Below are units of measurement commonly used in AP Chemistry. You will see these unit abbreviations used throughout the AP Chemistry exam.

### Atomic Structure

Atomic structure explores the makeup of an atom, its electronic structure, and what occurs during electronic transitions when a photon is absorbed or emitted. Equations and constants related to these ideas are provided in the Atomic Structure section of the AP Chemistry equation sheet.

**Energy of a photon equations**

**Equation (1)**shows how the energy*E*of a photon relates to Planck’s constant*h*, and frequency*ν*.**Equation (2)**relates the speed of light*c*to wavelength*λ*and frequency*ν*.

**Constants** (a numerical value that is always the same and does not change) such as Planck’s constant, Speed of light, Avogadro’s number, and electron charge are given.

### Equilibrium

Equilibrium focuses on reversible reactions, including some acid-base reactions, and how changing reaction conditions affects the direction of the reaction. Performing calculations involving the equilibrium constant *K* and understanding what the magnitude of *K* implies about equilibrium concentrations are essential for success on the AP Chemistry exam.

The Equilibrium section of the AP Chemistry formula sheet gives several equations necessary for problems involving equilibrium or acid-base chemistry.

**Equilibrium constant K equations**

*K*is defined as the ratio of either the equilibrium molar concentrations or partial pressures of the products over the reactants, where each is raised to the power of its corresponding stoichiometric coefficient (number in front of the product or reactant in the balanced reaction equation).**Equation (1)**defines*K*_{c}, the equilibrium constant when equilibrium molar concentrations are used.**Equation (2)**defines*K*_{p}, the equilibrium constant when partial pressures are used.

**Acid-base chemistry equations**

- The equilibrium constant for an acid or a base is the ratio of the equilibrium concentrations of the product ions to the unionized reactant. This value describes the strength of an acid or a base.
**Equation (3)**defines the acid equilibrium constant*K*_{a}.**Equation (4)**defines the base equilibrium constant*K*_{b}.**Equation (5)**shows the autoionization of water*K*_{w}.**Equation (6)**specifies how to calculate the acidity (pH) of a solution using the hydrogen ion concentration [H^{+}].**Equation (7)**shows how to calculate the basicity (pOH) of a solution using the hydroxide ion concentration [OH^{-}].**Equation (8)**shows how pH and pOH are numerically related.**Equation (9)**is the Henderson-Hasselbalch equation, which is derived from the*K*_{a}expression and uses pH, p*K*_{a}, and the ratio of the concentrations of the conjugate base [A^{-}] and acid [HA].**Equation (10)**shows how to express*K*_{a}in terms of p*K*_{a}.**Equation (11)**in this section shows how to express*K*_{b}in terms of p*K*_{b}.

### Kinetics

Kinetics focuses on reaction rate, or how fast a chemical reaction occurs. The reaction rate is described by the rate law, and the rate constant *k* used in rate law expressions is calculated by measuring the change in reactant concentration over time. The data obtained from measuring how reactant concentration changes over time are plotted in three ways, and one of the three graphs will be linear, indicating the reaction order.

The Kinetics section of the equation sheet on the AP Chemistry exam provides different equations you can use to calculate the rate constant *k*, depending on the order of the reaction.

**Integrated rate equations**

- Using
**Equation (1)**, you can calculate*k*for zero-order reactions. - Using
**Equation (2)**, you can calculate*k*for first-order reactions. - Using
**Equation (3)**, you can calculate*k*for second-order reactions.

**Half-life Equation**

- The half-life
*t*_{1/2}of a reaction is the amount of time it takes for the concentration of the reactants to be reduced by one-half. **Equation (4)**allows you to calculate*k*for first-order reactions if you know the*t*_{1/2}of the reaction.

### Gases, liquids, and solutions

Matter exists in different states (i.e., solid, liquid, or gas), and solids can be dissolved in a liquid to make a solution. The different states of matter and solutions exhibit different macroscopic (i.e., “large scale”) properties, such as pressure, density, temperature, and concentration.

The Gases, Liquids, and Solutions section of the AP Chemistry equation sheet contains several equations used to calculate different macroscopic properties for gases, liquids, and solutions and different constants used in these equations.

**Gas equations**

**Equation (1)**is the ideal gas law, which illustrates how an ideal gas behaves and is used to predict how a real gas behaves. The ideal gas law shows that pressure*P*and volume*V*are directly proportional to the number of moles of gas*n*and temperature*T*.**Equation (2)**uses the mole fraction*X*_{A}and the total pressure*P*_{total}in a container to calculate the partial pressure of one component*P*_{A}in the sample.**Equation (3)**shows that the total pressure P_{total}in a container is the sum of the partial pressure of each component (*P*_{A},*P*_{B}, etc) in the sample.**Equation (4)**shows how to calculate the number of moles*n*of a substance using the mass*m*and the molar mass*M*of that substance. This equation is not limited to being used in gas equations. Several different types of calculations require*n*, including the concentration of a solution.

**Molecular motion equations**

**Equation (5)**shows how to convert temperature*T*in degrees Celsius (°C) to Kelvin (K). This is important to know what to do for equations that require Kelvin temperature, such as the ideal gas law.**Equation (7)**indicates how mass*m*and velocity*v*are used to calculate the kinetic energy*KE*of a molecule.

**Solution equations**

**Equation (6)**shows that the density D of a substance is a ratio of mass m to volume V.**Equation (8)**describes how to calculate the concentration (molarity) of a solution using the number of moles of solute and the volume of the solution.**Equation (9)**in this section is Beer’s Law, which is used in UV-vis spectroscopy (measuring the absorbance of UV-vis light by a solution at different wavelengths). Beer’s Law describes the relationship between the absorbance A, molar absorptivity ε, path length b of the container through which the light passes through, and concentration of the solution c.

**Constants**

Three values of the gas constant *R* (used in the ideal gas law) are given. The only difference between each value is the units of pressure. You can use any of these values in the ideal gas law equation as long as the units of pressure for the value of *R* used match the units of pressure for *P*.

The conditions of STP (standard temperature and pressure) and the molar volume of an ideal gas at STP are also given.

### Thermodynamics/electrochemistry

Thermodynamics focuses on the relationship between Gibbs free energy *G*, enthalpy *H*, and entropy *S*, and how the change in standard Gibbs free energy Δ*G *° relates to the favorability of a chemical reaction.

Electrochemistry covers galvanic and electrolytic cells, how to determine the standard cell potential *E *° and free energy of the cell, and how to apply the Nernst equation and Faraday’s law.

The final section of the AP Chemistry formula sheet contains several equations and constants used in problems related to thermodynamics and electrochemistry.

**Thermodynamics equations**

**Equation (1)**is used to determine the amount of heat*q*absorbed or released by a substance and requires knowing the mass of the substance*m*, specific heat capacity of that substance*c*, and the change in temperature Δ*T*(ie,*T*_{final}−*T*_{initial}) in ℃. This equation is often used in calorimetry problems.**Equation (2)**shows that the standard entropy change Δ*S*° for a reaction is calculated by subtracting the sum of the standard entropies of the products*S*°_{products}from the sum of the standard entropies of the reactants*S*°_{reactants}.**Equation (3)**is used to calculate the standard enthalpy change Δ*H*° for a reaction. Δ*H*° is determined by subtracting the sum of the standard enthalpies of formation of the products Δ*H*_{f}°_{products}from the sum of the standard enthalpies of formation of the reactants Δ*H*_{f}°_{reactants}.**Equation (4)**shows that the standard Gibbs free energy change Δ*G*° for a reaction is found by subtracting the sum of the standard free energy of formation of the products Δ*G*_{f}°_{products}from the sum of the standard free energy of formation of the reactants Δ*H*_{f}°_{reactants}.- Don’t forget to multiply the values of
*S*°, Δ*H*_{f}° , and Δ*G*_{f}° for products and reactants by the stoichiometric coefficient from the balanced reaction equation. **Equation (5)**relates the standard gibbs free energy change Δ*G*° to the changes in enthalpy Δ*H*°, entropy Δ*S*°, and temperature Δ*T*.**Equation (6)**relates the standard gibbs free energy change Δ*G*° and the equilibrium constant*K*.

**Electrochemistry equations**

**Equation (7)**shows how to calculate Δ*G*° of an electrochemical cell using the the number of electrons transferred*n*, Faraday’s constant*F*, and the standard cell potential*E*°.**Equation (8)**gives the relationship between current*I*, charge*q*, and time*t*. This equation is used along with Faraday’s law in problems involving electrolysis.**Equation (9)**is the Nernst equation, which is used to determine E_{cell}under nonstandard conditions (standard conditions are solution concentrations of 1 M, a system pressure of 1 atm, and temperature of 25 ℃).

**Constants**

*F*, which is used in some calculations of Δ

*G*° and the Nernst equation, is given. The relationship between volts, joules, and coulombs is given.

## Periodic Table of Elements

You are also given a periodic table of elements to reference on the AP Chemistry exam. The periodic table includes valuable information that you will use to solve various problems on the exam. Below are the components contained in each square on the periodic table and some features of the AP Chemistry periodic table you should be familiar with for exam day.

- Each square on the periodic table contains
- The
**atomic number**at the top of the square. This value corresponds to the number of protons in the nucleus. - The unique one- or two-letter
**chemical symbol**for the corresponding element in the center of the square. - The
**atomic mass (molar mass)**, which has units of amu or g/mol, is found at the bottom of the square. This value tells you the mass of one mole of the element.

- The
- The
**group number**is located at the top of each column on the periodic table.

Congratulations! You’ve completed the review of important equations, constants, and parts of the periodic table on the equation sheet given to you on the AP Chemistry exam. You will be prepared to solve problems using the equation sheet with confidence and expertise! Just remember, to succeed on the AP Chemistry exam, it is important to know both the layout of the formula sheet and how to apply the equations and constants to any mathematical problems you encounter.