AP Chemistry · Summary

Unit 7 summary

1. At equilibrium the forward and reverse rates are equal, so concentrations are constant, not equal.
2. K is products over reactants with coefficients as exponents; leave out pure solids and liquids. Reverse the equation: 1/K. Multiply coefficients by n: $K^n$. Add equations: multiply the K values.
3. Find K from equilibrium molarities only: convert moles to molarity, then use an ICE table tied together by the coefficients.
4. Q has the same form as K with current values. Q below K: the net reaction runs forward. Q above K: it runs in reverse.
5. A change in amount, or in volume when the moles of gas differ, moves Q away from K; a temperature change gives a new K; a catalyst or an inert gas at constant volume changes neither.
6. Heating raises K for an endothermic reaction and lowers it for an exothermic one; a smaller volume shifts toward fewer moles of gas.
7. For $\text{MX}$, $K_{sp} = s^2$; for $\text{MX}_2$, $K_{sp} = 4s^3$. A common ion lowers solubility, acid raises the solubility of salts with basic anions, and $Q > K_{sp}$ means a precipitate forms.