RP9- Effect Of Strong And Weak Acids/bases On PH

Question 1

Describe a method to create a pH probe calibration

Answer 1

Rinse a pH probe with de-ionised water, shake it gently to remove any excess water

Place the pH probe in a standard pH 7 solution, ensuring the bulb is fully immersed. Record the pH on the probe
Repeat with standard buffer pH solutions of 4 and 9.2

Draw a graph with pH recorded on the x axis, and pH of the standard solutions on the y-axis

Question 2

What is a pH probe calibration curve used for?

Answer 2

To convert pH readings into more accurate pH values

Question 3

Describe a method to measure the pH of a mixture?

Answer 3

Rinse a burette with ethanoic acid, use it to transfer 20cm3 of ethanoic acid to a beaker

Rinse a second burette with NaOH, fill the burette with this solution. Ensure there are no air bubbles.

Rinse a pH probe with de- ionised water and clamp it in place so the bulb is immersed in the ethanoic acid

Use a glass rod to stir the solution, measure the initial pH

Use the burette to add NaOH, 2cm3 at a time. Record the pH each time

When it is close to the end point, add the NaOH at 0.2cm3 each time. After this add 2cm3 at a time until NaOh is in excess

Plot a pH curve using the data