So,
We'll begin by calculating the concentration of Hydrogen ion in the resulting solution. This can be obtained using the definition of pH:
Replacing our value for pH, we're going to solve for [H3O+]:
Next, we shall determine the molarity of the resulting solution of HBr.
When HBr dissociates, the following reaction takes place:
From the balanced equation above, we can notice that 1 mole of HBr contains 1 mole of H⁺
Therefore, 3.71×10¯⁴ M HBr will also contain 3.71×10¯⁴ M H⁺.
Finally, we shall determine the volume of the stock solution of HBr needed to prepare the solution. From the values of the problem, we know that:
Molarity of stock solution (M₁) = 8.84 M
Volume of diluted solution (V₂) = 300 mL
Molarity of diluted solution (M₂) = 3.71×10¯⁴ M
Volume of stock solution needed (V₁) = ?
Using the following equation, we could solve for V1:
Therefore, 0.013 mL of 8.84M HBr would be needed.