Final answer:
At pH 3, the concentration of H+ ions is 1 x 10^-3 M, which denotes an acidic solution. The pH value is determined by the negative logarithm of the hydrogen ion concentration, and a pH below 7 is considered acidic.
Step-by-step explanation:
The question pertains to the relationship between pH and hydrogen ion concentration in solutions. At pH 3, the concentration of H+ ions is 1 x 10-3 molar, which indicates an acidic solution. The pH scale is logarithmic, hence a pH of 3 indicates a hydrogen ion concentration ten times greater than a pH of 4. The negative logarithm of the H+ ion concentration gives the pH value, so for a concentration of 1 x 10-3 M, the pH is 3.
To provide more context, in pure water at 25 °C, the concentration of H+ is 1 x 10-7 M, which corresponds to a pH of 7, considered neutral. Anything lower than pH 7 is acidic, and higher is basic or alkaline. It is important to note that the product of the concentrations of H+ and OH- ions in water is always 1.0 x 10-14 at 25 °C.