Question: How to calculate the H3O of a solution with a pOH of 5,3?
1. **State the problem:** We need to find the concentration of hydronium ions $\mathrm{H_3O^+}$ given the pOH of the solution is $5.3$.
2. **Recall the relationship between pH and pOH:**
$$\mathrm{pH} + \mathrm{pOH} = 14$$
This is a fundamental rule for aqueous solutions at 25°C.
3. **Calculate the pH:**
$$\mathrm{pH} = 14 - 5.3 = 8.7$$
4. **Use the pH to find $\mathrm{[H_3O^+]}$ concentration:**
The formula relating pH and hydronium ion concentration is:
$$\mathrm{pH} = -\log_{10} [\mathrm{H_3O^+}]$$
Rearranged to solve for $[\mathrm{H_3O^+}]$:
$$[\mathrm{H_3O^+}] = 10^{-\mathrm{pH}}$$
5. **Calculate $[\mathrm{H_3O^+}]$:**
$$[\mathrm{H_3O^+}] = 10^{-8.7}$$
6. **Evaluate the value:**
$$10^{-8.7} \approx 2.0 \times 10^{-9}$$
**Final answer:** The hydronium ion concentration is approximately $2.0 \times 10^{-9}$ mol/L.
This means the solution is basic since pH is greater than 7.