Chemical Reactions and Stoichiometry

Synthesis (Combination)

$\text{A} + \text{B} \rightarrow \text{AB}$

Decomposition

$\text{AB} \rightarrow \text{A} + \text{B}$

Single Replacement

$\text{A} + \text{BC} \rightarrow \text{AC} + \text{B}$ (Activity series determines if reaction occurs)

Double Replacement (Metathesis)

$\text{AB} + \text{CD} \rightarrow \text{AD} + \text{CB}$ Driving forces: precipitate formation, water formation, gas formation

Combustion

$\text{Hydrocarbon} + \text{O}_2 \rightarrow \text{CO}_2 + \text{H}_2\text{O}$

Oxidation-Reduction (Redox)

Electron transfer; one species oxidised, another reduced.

1. Write the balanced molecular equation
2. Split all soluble strong electrolytes into ions
3. Cancel spectator ions (identical on both sides)
4. What remains is the net ionic equation

Example: $\text{AgNO}_3(aq) + \text{NaCl}(aq) \rightarrow \text{AgCl}(s) + \text{NaNO}_3(aq)$ $\text{Ag}^+(aq) + \text{Cl}^-(aq) \rightarrow \text{AgCl}(s)$

Steps

1. Write balanced equation
2. Convert given to moles: $n = m/M$ or $n = cV$
3. Use molar ratio to find moles of target
4. Convert to desired units

Limiting Reagent

The reactant that produces the LEAST amount of product. Determines maximum yield.

Percent Yield

$\%\text{yield} = \frac{\text{actual yield}}{\text{theoretical yield}} \times 100$

Gravimetric: measure mass of precipitate to determine amount of ion Volumetric (Titration): measure volume of known solution to find unknown concentration

• Reaction types: synthesis, decomposition, single/double replacement, combustion, redox
• Net ionic equations: remove spectator ions
• Stoichiometry: balanced equation → mole ratio → convert
• Limiting reagent determines theoretical yield
• % yield = actual/theoretical × 100