 # how to calculate ph problems?

9 years ago
pH - A measure of the hydrogen ion concentration, it is equal to - log [H+].
Calculating the pH of Strong Acid and Strong Base Solutions
When a strong acid or a strong base is added to water, it nearly completely dissociates into its ion constituents because it has a pK a or pK b less than zero. For example, a solution of H2SO4 in water contains mostly H+ and SO4 2-, and almost no H2SO4 is left undissolved. This makes calculating the pH of a strong acid or strong base solution exceedingly simple
The concentration of acid equals the concentration of H+and pH is computed by taking the negative log of [H+].
Calculating the pH of Weak Acid and Weak Base Solutions

Calculating the pH of weak acid and weak base solutions is much more complicated than the above case--weak acids and bases do not completely dissociate in aqueous solution but are in equilibrium with their dissociated forms. Therefore, we must apply what we know about equilibria to solve these types of problems. For example, let's calculate the pH of a 0.10 M solution of acetic acid in water. To do this, we first write down the equilibrium involved and the expression for the equilibrium constant: This is how pH can be calculated.

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Aarti Gupta