Final answer:
The pH of pure water is 7 option (d), making it neutral, while coffee is acidic with a pH ranging from 5.0 to 5.5. The pH difference of 1 to 2 indicates coffee is 10 to 100 times more acidic than pure water.
Step-by-step explanation:
When comparing the pH of pure water and coffee, we must consider the pH scale and how pH is measured. Pure water is neutral with a pH of 7. On the other hand, coffee is typically acidic and has a pH that usually falls near the range of 5.0 to 5.5. This means the pH of coffee differs from pure water by approximately 1 to 2 units, depending on the specific acidity of the coffee.
It is important to remember that the pH scale is logarithmic, where each whole number difference represents a tenfold change in the concentration of hydronium ions. Therefore, the pH difference indicates that the hydronium ion concentration in coffee is about 10 to 100 times higher than in pure water. Given the choice of answers, we would select option (a) 1-2 as the approximate pH difference between pure water and coffee.