What has a pH of 13?

Answer C is correct. Generally speaking, when you are considering the correlation of an aqueous solution of an acid and of a base the higher the pH level, then the stronger (or more acidic) the acid will be.

Alternatively, if the acid have a lower pH value, then the base will be weaker than one with a higher pH balance. Since the pH value is a measurement of how many hydrogen ions are present in the solution. The more hydrogen ions in the solution, the higher the pH and therefore the more acidic the solution will be.

The pH is the short term for power of hydrogen. It shows the strength or the concentration of hydrogen ions in solution. Hence it is commonly used as an indicator of acidity or alkalinity of a solution. In this case, there are different terms that implement different situations. Generally speaking, the higher the pH the higher the acidity of the solution as the power of hydrogen is more.

Moreover, the lower the pH, the weaker is the base. You can memorize this as a rule because it stays constant and is required in numerous aspect of life. Having basic knowledge of this important concept is vital for every student of the modern world.