THREE DROPS OF A 1.0 MOL DM-3 SOLUTION OF NAOH ARE ADDED TO 20 CM3 OF A SOLUTION OF PH 8.4. THE PH OF THE RESULTING SOLUTION WILL

• A. Close to that of pure water
• B. Unaltered
• C. Greater than 8.4 ✓
• D. Less than 8.4

The answer to the question is: C. Greater than 8.4

When three drops of a 1.0 mol dm-3 solution of NaOH are added to 20 cm3 of a solution with a pH of 8.4, the resulting pH of the solution will be greater than 8.4. This is because NaOH is a strong base and when it is added to the solution, it will react with the water to produce hydroxide ions (OH-) which will increase the concentration of hydroxide ions in the solution, leading to an increase in pH.

The addition of NaOH to the solution will result in a neutralization reaction, where the hydroxide ions from NaOH will react with the hydrogen ions (H+) present in the solution. This reaction will lead to an increase in the concentration of hydroxide ions and a decrease in the concentration of hydrogen ions, causing the pH to increase.

The pH scale is logarithmic, so even small changes in the concentration of hydrogen ions or hydroxide ions can result in significant changes in pH. In this case, the addition of a strong base like NaOH will lead to a substantial increase in the concentration of hydroxide ions, causing the pH of the resulting solution to be greater than 8.4.