Which tool is known for providing the exact pH of a solution?

The pH probe is the correct choice for providing the exact pH of a solution because it is a specialized instrument designed to measure the hydrogen ion concentration in the solution directly. This tool typically consists of a glass electrode that interacts with the solution, generating a voltage that correlates with the pH level. The output from the probe is usually displayed digitally, offering precise readings that are essential for scientific applications where accuracy is necessary.

In contrast, litmus paper and universal indicators are qualitative tools that provide a general idea of whether a solution is acidic or basic, but they cannot deliver exact pH values. Litmus paper changes color at certain pH levels, while universal indicator shows a range of colors corresponding to a pH scale, but both tools lack the precision of a pH probe. A conductivity meter measures the electrical conductivity of a solution, which can give information about ion concentration but not specifically pH. Therefore, the pH probe is uniquely suited for determining the exact pH of a solution.