What is the normal pH value?
pH is the measure of the concentration of protons in a solution (usually water). It is mathematically defined as:
pH = -log[H+]
This means that the pH of a solution is the negative log of the concentration of protons in moles per liter. pH is in essence a measure of the acidity or basicity of a solution. It is based on a standard scale of 0 to 14 with 0 being the most acidic and 14 being the least acidic (most basic). Since it is a logarithmic scale, a difference of one pH unit is really an order of magnitude difference.
There is no truly "normal" pH value. A pH of 7 is a completely neutral solution (equal concentrations of H+ and OH-). It is neither acidic nor basic. Normal drinking water is usually slightly acidic in nature (around pH 6). So I suppose the answer you are looking for is either 7 or slightly below that.