Determine the pH for the following solutions:
c. [H₃O⁺] = 0.0001 M

Verified step by step guidance

1. Step 1: Recall the formula for calculating pH, which is given by: $\mathrm{pH}=-\log \left({\mathrm{[H}}_3\right])$. This formula relates the hydronium ion concentration to the pH of the solution.
2. Step 2: Identify the given value for the hydronium ion concentration, ${\mathrm{[H}}_3]$, which is 0.0001 M.
3. Step 3: Substitute the given value of ${\mathrm{[H}}_3$ into the pH formula: $\mathrm{pH}=-\log \left(0.0001\right)$.
4. Step 4: Simplify the logarithmic expression. Recall that $\log (10^-4)$ simplifies to -4, so $-\log \left(0.0001\right)$ becomes 4.
5. Step 5: Conclude that the pH of the solution is equal to 4. This indicates that the solution is acidic, as pH values less than 7 correspond to acidic solutions.

Key Concepts

pH Scale

The pH scale measures the acidity or basicity of a solution, ranging from 0 to 14. A pH of 7 is considered neutral, while values below 7 indicate acidity and values above 7 indicate alkalinity. The scale is logarithmic, meaning each whole number change represents a tenfold change in hydrogen ion concentration.

Hydronium Ion Concentration

Hydronium ions (H₃O⁺) are formed when an acid donates a proton to water. The concentration of hydronium ions in a solution directly influences its pH. For example, a higher concentration of H₃O⁺ results in a lower pH, indicating a more acidic solution.

Calculating pH

To calculate pH from hydronium ion concentration, the formula pH = -log[H₃O⁺] is used. This formula allows for the conversion of the molarity of hydronium ions into a pH value. For instance, if [H₃O⁺] = 0.0001 M, the pH can be calculated as 4, indicating an acidic solution.