Activity 4.4

Acids, bases and pH

which solution acted as a buffer and why?

organisms to keep solutions at a relatively constant pH. By releasing or absorbing H+, and slight chat changes in pH. For example, human blood contains buffers that maintain a pH of 7.37.5 and changes in the pH of blood could result in complications or even death. Exercise 4.4a: Which is the Buffer? Materials needed: sodium bicarbonate, sodium chloride, acetic acid, pH strips, two 50-mL beakers, 10-mL graduated cylinder, scissors, scale, weigh boat, gloves, safety goggles 1. Record your observations and results in the area below. 2. Cut pH paper into 2cm strips while wearing gloves. 3. Weigh out 0.5 grams of sodium bicarbonate (NaHCO3) and transfer to a beaker. Do the same with the sodium chloride ( NaCl). 4. Measure 10mL of water in the graduated cylinder, pour into the beaker containing the sodium bicarbonate, and swirl to mix. Repeat this process with the sodium chloride. 5. Test the pH of both solutions. 6. Measure 10mL of acetic acid (CH3COOH) in the graduated cylinder. Test the pH of acetic acid. 7. Pour 5mL of acetic acid into the beaker containing the solution of NaHCO3. 8. Pour the remaining 5mL of acetic acid into the beaker containing the NaCl solution. 9. Test the pH of both solutions and record in the Observations section. 10. Wash all glassware and return items to your kit. - Observations: - Which solution acted as a buffer and why