Calculate the pH of a 25 mL of 5.45 × 10 − 2 M LiOH solution.

Calculate the pH of 25 ml's of 5.45 times 10 to the negative 2 molar lithium hydroxide solution. Now, lithium hydroxide represents a strong base, and what we need to see here is that we have both the volume and the concentration of my strong base. But here's the thing, we don't need to use the volume. We only use the volume of this base if it were being titrated with an acid. That volume is just placed there to kind of throw you off. Because it's just a base by itself, we focus on the concentration. Here, when it ionizes completely it breaks up into lithium ion plus 1 hydroxide ion. Here, each of these ions would have the same concentration as the strong base itself. And since there's only 1 hydroxide ion here, it'd just be 5.45 times 10 to the negative 2 molar. So we know the concentration of my hydroxide ion. With that information I can first find pOH. Remember pOH equals negative log of Oh minus, So it's equal to negative log of 5.45 times 10 to the negative 2. When I put that into my calculator I'm gonna get 1.264 as my pOH. Now that we know our pOH we can find our pH, because they're connected together by the fact that pH, plus pOH equals 14. So, here when I subtract pOH from both sides we see that pH equals 14 minuteus pOH. So plug in what we just found for pOH and we'll have our answer. So, 14 minuteus 1.264 gives me 12.736 as the pH for this very strong base. It's a pretty concentrated strong base, so we'd expect the pH to be pretty high.

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17. Acid and Base Equilibrium

pH of Strong Acids and Bases

General Chemistry

17. Acid and Base Equilibrium

pH of Strong Acids and Bases

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Multiple Choice

Calculate the pH of a 25 mL of 5.45 × 10⁻² M LiOH solution.

1.264

12.736

0.338

11.134

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Verified step by step guidance

Start by understanding that LiOH is a strong base, which means it dissociates completely in water. Therefore, the concentration of OH⁻ ions in the solution is equal to the concentration of LiOH.

Use the formula for pOH: \( \text{pOH} = -\log[\text{OH}^-] \). Substitute the concentration of OH⁻ ions, which is 5.45 × 10⁻² M, into this formula to find the pOH.

Recall the relationship between pH and pOH: \( \text{pH} + \text{pOH} = 14 \). Use this equation to solve for the pH once you have calculated the pOH.

Substitute the calculated pOH value into the equation \( \text{pH} = 14 - \text{pOH} \) to find the pH of the solution.

Ensure that your final pH value makes sense for a basic solution, as LiOH is a strong base. The pH should be greater than 7.