Calculations involving acids and bases

Calculations Involving Acids and Bases

pH and pOH Calculations

The pH scale is a logarithmic scale that measures the acidity or alkalinity of a solution. It ranges from 0 (highly acidic) to 14 (highly alkaline), with 7 being neutral.
The pH of a solution can be calculated using the formula pH = -log[H+], where H+ is the concentration of hydrogen ions in moles per litre.
The pOH of a solution is similar to pH but is concerned with hydroxide ions (OH-) instead of hydrogen ions. It can be calculated using the formula pOH = -log[OH-].
The pH and pOH are inversely related: pH + pOH = 14 at 25°C.

Molarity Calculations

Molarity (M) is a measure of the concentration of a solute in a solution, or its mole-litre ratio.
To calculate molarity, use the formula M = moles of solute / litres of solution.
If you know the molarity of an acid or base and the volume of the solution, you can calculate the number of moles of the acid or base using the formula moles = Molarity (M) x Volume (L).

Neutralisation Reactions

In a neutralisation reaction, an acid reacts with a base to produce salt and water. At the equivalence point of a strong acid-strong base titration, the pH is 7.
The mole ratio of acid to base in a neutralisation reaction is determined by the balanced chemical equation for the reaction.
To determine the volume or concentration of acid or base needed to neutralize each other, you should use the formula moles of acid = moles of base.
Given the volume and concentration of one solution, and the volume of another, you can calculate the unknown concentration using the formula MaVa = MbVb, where Ma and Mb are the molarities of the acid and base, respectively, and Va and Vb are their volumes.

Buffers

A buffer is a solution that resists changes in pH when small amounts of an acid or a base are added, or when the solution is diluted.
The pH of a buffer can be calculated using the Henderson-Hasselbalch equation: pH = pKa + log([A-]/[HA]) where [A-] represents the molar concentration of the ion formed by deprotonation of the acid, [HA] represents the molar concentration of the undissociated acid and pKa is the acid dissociation constant.