Calculate Concentrations in a Buffer (Example Problem)

The video tutorial explains how to calculate the number of moles of conjugate acid and base in a phosphate buffer solution using the Henderson-Hasselbalch equation. It covers the setup of a buffer problem, the calculation of moles for both conjugate acid and base, and the conversion of these moles into mass for practical lab preparation. The tutorial also discusses how to verify calculations by comparing pH and pKa values, ensuring the buffer is prepared correctly.

What is the formula used to calculate the number of moles of conjugate acid in a buffer solution?

• Volume of buffer divided by concentration of buffer

• Concentration of buffer times volume of buffer

• 10 to the power of pH minus pKa

• Concentration of buffer times volume of buffer divided by 10 to the power of pH minus pKa plus 1

Which pKa value should be used when preparing a buffer at pH 7?

• 2.12

• 7.21

• 12.67

• None of the above

What is the significance of the pKa value in buffer preparation?

• It is irrelevant to buffer preparation

• It indicates the buffer's temperature

• It helps in selecting the appropriate acid-base pair

• It determines the buffer's color

What is the first step in calculating the number of moles of conjugate base?

• Add moles of conjugate acid to total buffer concentration times volume

• Subtract moles of conjugate acid from total buffer concentration times volume

• Multiply moles of conjugate acid by total buffer concentration

• Divide moles of conjugate acid by total buffer concentration

If the moles of conjugate acid are greater than the moles of conjugate base, what can be inferred about the pH?

• pH is neutral

• pH is higher than pKa

• pH is lower than pKa

• pH is equal to pKa

Why is it important to convert moles into mass when preparing a buffer in the lab?

• Mass is easier to measure with an analytical balance

• Moles cannot be converted to grams

• Moles are not useful in calculations

• Mass provides more accurate results

How do you calculate the mass of the conjugate acid needed for buffer preparation?

• Multiply moles of conjugate acid by its molecular weight

• Divide moles of conjugate acid by its molecular weight

• Subtract moles of conjugate acid from its molecular weight

• Add moles of conjugate acid to its molecular weight