Equipment:

• 100 ml beaker
• 20 ml of milk
• 3 drops of BTB
• 1 bottle of [[$\text{HCl(aq)}$]]
• 1 bottle of [[$\text{NaOH(aq)}$]]
• 10 slips of pH paper
• 1 tissue

Instructions:

1. Add 15 drops of [[$\text{HCl}$]] into the solution, one drop at a time.
2. Measure the pH of the solution with a slip of pH paper.
3. Place the slip on the tissue.
4. Add 3 drops of [[$\text{NaOH}$]] into the solution.
5. Repeat from step 1 onwards until the pH slips are exhausted.
6. Plot the pH changes as a diagram.
   • horizontal: drops of [[$\text{NaOH}$]]
   • vertical: pH of solution
   • With a trendline, find the amount of [[$\text{NaOH}$]] drops needed for pH 7.