Answer to Question #306749 in General Chemistry for UN_KNOWN

Question

Prepare 100 mL of 0.200 bicarbonate buffer, pH 10 by calculating the mass of sodium bicarbonate and sodium carbonate. 

a. Use the Henderson-Hasselbalch equation to calculate the volume of each stock

solution needed.

pH = pKa + log [conjugate base] / [weak acid]1

b. Check your calculations with other students. See the instructor if there is uncertainty.

c. Make the solution and check the pH of a portion of your buffer solution using the pH

meter.

L = 245μL 

solution:

Preparation of Bicarbonate Buffer

Calculated Volume

CH₃COOH ____________________

KH₂PO4 ____________________

Actual pH of the buffer: ____________________

Answer 1

100 ml × 0.2 = 20 ml

Molar mass of sodium carbonate = 105.9888 g/mol

Molar mass of sodium bicarbonate = 84.007 g/mol

= 105.9888 × 84.007/20

= 4.452 × 102

= log 4.452 × 102 = 2.65

pH = 10 + 2.65 = 12.65