General Chemistry Stoichiometry and Solutions Cheat Sheet

Key Facts

• The mole conversion between mass and amount is $n = \frac{m}{M}$, where $n$ is moles, $m$ is mass, and $M$ is molar mass.
• Stoichiometric mole ratios come only from coefficients in the balanced equation, such as $aA + bB \rightarrow cC + dD$ giving $\frac{c\ \text{mol C}}{a\ \text{mol A}}$.
• The limiting reactant is the reactant that produces the smaller calculated amount of product, and theoretical yield is based on that reactant.
• Percent yield is calculated by $\%\ \text{yield} = \frac{\text{actual yield}}{\text{theoretical yield}} \times 100\%$.
• Molarity is $M = \frac{n}{V}$, where $V$ must be in liters and $M$ has units of $\text{mol}\ \text{L}^{-1}$.
• Dilution problems use $M_1V_1 = M_2V_2$ because the moles of solute stay constant when only solvent is added.
• The ideal gas law is $PV = nRT$, with consistent units such as $R = 0.08206\ \text{L}\ \text{atm}\ \text{mol}^{-1}\ \text{K}^{-1}$.
• Real gases deviate most from ideal behavior at high pressure and low temperature, and the van der Waals equation is $\left(P + a\frac{n^2}{V^2}\right)(V - nb) = nRT$.

Vocabulary

Stoichiometry

Stoichiometry is the use of balanced chemical equations to calculate relationships between reactants and products.

Limiting Reactant

The limiting reactant is the reactant that is consumed first and determines the maximum amount of product that can form.

Theoretical Yield

The theoretical yield is the maximum product amount predicted by stoichiometry from the limiting reactant.

Molarity

Molarity is the concentration of a solution defined as moles of solute per liter of solution, $M = \frac{n}{V}$.

Dilution

Dilution is the process of lowering solution concentration by adding solvent while keeping the moles of solute constant.

Ideal Gas

An ideal gas is a model gas whose particles have negligible volume and no intermolecular attractions, so it follows $PV = nRT$.