An acid solution is best defined as a solution that has a higher concentration of hydrogen ions (H+) than pure water. This means that the pH value of an acid solution is less than 7, with 7 being the neutral pH value. Acid solutions are characterized by their sour taste, corrosive nature, and ability to react with certain metals to produce hydrogen gas. Acids can be either strong or weak, with strong acids completely dissociating in water to release all of their hydrogen ions, while weak acids only partially dissociate. Common examples of acids include hydrochloric acid (HCl), sulfuric acid (H2SO4), and citric acid (a natural acid found in citrus fruits).