Berapakah harga pH larutan campuran 100 mL larutan 0,6 M CH_(3) COOH dengan 100 mL larutan ...

Summary

This video explains how to calculate the pH of a buffer solution formed by mixing acetic acid (CH3COOH) with barium hydroxide (Ba(OH)2). It walks through the step-by-step process of determining the limiting reagent, performing the chemical reaction, and identifying the leftover weak acid and its conjugate base, forming a buffer. The formula for buffer solutions is then applied to calculate the concentration of H+ ions and, subsequently, the pH. The final pH is found using the -log of the H+ concentration, resulting in a value close to 6.

Takeaways

• 🧪 The problem asks for the pH of a solution mixing 100 ml of 0.6 M CH3COOH with 100 ml of 0.2 M Ba(OH)2, with Ka of CH3COOH given as 1.6 * 10^-5.
• 📏 Moles of CH3COOH are calculated as 60 mmol (0.6 M * 100 ml).
• 📏 Moles of Ba(OH)2 are calculated as 20 mmol (0.2 M * 100 ml).
• ⚖️ The reaction is 2 CH3COOH + Ba(OH)2 → Ba(CH3COO)2 + 2 H2O.
• 🔍 Ba(OH)2 is identified as the limiting reagent because 20 mmol / 1 (Ba(OH)2) < 60 mmol / 2 (CH3COOH).
• 🔬 Ba(OH)2 reacts completely, leaving 20 mmol CH3COOH unreacted and forming 20 mmol Ba(CH3COO)2.
• 🧫 A buffer solution is formed consisting of the weak acid (CH3COOH) and its conjugate base (CH3COO- from Ba(CH3COO)2).
• 📊 The concentration of H+ ions is calculated using the buffer equation: [H+] = Ka * [weak acid] / [conjugate base].
• 🧮 [H+] = (1.6 * 10^-5) * (20 mmol) / (40 mmol) = 8 * 10^-6 M.
• 📉 The pH of the solution is calculated as pH = -log[H+] = 6 - log 8, giving a pH close to 6.

Q & A

What is the first step in calculating the pH of the mixture in this problem?

The first step is to determine the moles of CH3COOH and Ba(OH)2 by multiplying their molarity by the volume.

How many moles of CH3COOH are present in the mixture?

There are 60 mmol of CH3COOH, calculated by multiplying 0.6 M by 100 mL.

How many moles of Ba(OH)2 are present in the mixture?

There are 20 mmol of Ba(OH)2, calculated by multiplying 0.2 M by 100 mL.

What is the limiting reagent in the reaction, and how is it determined?

Ba(OH)2 is the limiting reagent, determined by comparing the moles divided by the stoichiometric coefficient (Ba(OH)2 gives 20/1 = 20, CH3COOH gives 60/2 = 30).

How much CH3COOH reacts in the mixture?

A total of 40 mmol of CH3COOH reacts with Ba(OH)2.

How many mmol of CH3COOH remain after the reaction?

There are 20 mmol of CH3COOH remaining after the reaction.

What is formed after the reaction between CH3COOH and Ba(OH)2?

The reaction forms Ba(CH3COO)2 (20 mmol) and water (40 mmol).

Why is the resulting solution considered a buffer solution?

The solution is considered a buffer because it contains a weak acid (CH3COOH) and its conjugate base (CH3COO-), formed from the salt.

How do you calculate the concentration of H+ in this buffer solution?

The concentration of H+ is calculated using the formula: [H+] = Ka * (mol of weak acid) / (mol of conjugate base).

What is the pH of the buffer solution, and how is it calculated?

The pH is calculated as -log[H+], which results in a pH of approximately 6 - log(8).