How to Make and pH Buffers

Summary

In this video, Dan demonstrates how to make a buffer solution and adjust its pH. Starting with 500 mL of water in a beaker, he adds the buffer ingredients and gradually pours in concentrated hydrochloric acid to bring the pH down from 10.69 to 8.8. Throughout the process, he explains the importance of the buffer's range and how pH changes quickly before stabilizing. Once the desired pH is achieved, Dan tops off the solution to 500 mL, completing the buffer preparation. The video offers clear instructions on making a buffer solution and adjusting its pH effectively.

Takeaways

• 😀 Always remember that solid substances also have volume, which can affect the final volume of a solution.
• 😀 To make a buffer, start by gathering all necessary ingredients and prepare the beaker for mixing.
• 😀 A buffer solution is typically prepared by adding water to a set volume of ingredients. In this case, 500 mL is the target volume.
• 😀 The initial pH of the buffer is typically high, in this case around 10.69, before adjusting it to the desired pH range.
• 😀 When adjusting the pH of a buffer, use a strong acid like concentrated hydrochloric acid to gradually lower the pH.
• 😀 It is important to add the acid slowly, drop by drop, as the pH will change rapidly when it’s outside the buffer's effective range.
• 😀 Once the pH reaches the buffering range, the change in pH becomes slower and more stable.
• 😀 The target pH for this particular buffer is 8.8, which is achieved after gradual acid addition.
• 😀 After reaching the desired pH, the buffer solution should be topped off with water to the desired volume, in this case, 500 mL.
• 😀 Make sure to add the remaining water slowly and carefully, using a graduated cylinder for accurate measurement.

Q & A

What is the first step in making a buffer according to the script?

The first step is gathering the ingredients, followed by pouring them into a beaker.

How much volume of water was initially in the beaker?

There was initially 500 mL of water in the beaker.

Why does adding solid to the buffer affect its volume?

Adding solid increases the volume of the solution, as solids also occupy space.

What is the purpose of adding hydrochloric acid to the buffer?

The hydrochloric acid is added to lower the pH of the buffer to the desired value, in this case, 8.8.

What is the initial pH of the buffer in the script?

The initial pH of the buffer is about 10.69.

At what pH is the buffer considered to be in the buffering range?

The buffer is in the buffering range when its pH is around 8.8.

How is the pH of the buffer adjusted in the script?

The pH is adjusted by slowly adding concentrated hydrochloric acid drop by drop.

What happens to the pH change rate when it enters the buffering range?

Once the pH enters the buffering range, the pH change slows down.

How does the volume of the buffer change during the process?

The volume of the buffer is first adjusted to about 360 mL and then topped off to 500 mL using water.

What tool is used to measure and add water to adjust the buffer's final volume?

A graduated cylinder is used to add water gradually until the buffer reaches 500 mL.