Final answer:
After neutralizing 99.9% of an acid with a starting pH of 1, the pH value becomes approximately 4.00, not 6.7, due to the 0.1% remaining hydrogen ion concentration.
Step-by-step explanation:
To approximate the pH of a solution resulting from the neutralization of 99.9% of an acid starting with a pH of 1, we can use some background knowledge of pH and hydrogen ion concentration. The pH scale ranges from 0 to 14, where 7 represents a neutral solution, below 7 is acidic, and above 7 is basic. The pH is also a logarithmic scale, meaning each unit change represents a tenfold change in hydrogen ion concentration.
As a starting point, a pH of 1 corresponds to a hydrogen ion concentration of 1.0 x 10-1M. Neutralizing 99.9% of the acid essentially leaves 0.1% of the original concentration. Since 10-3 is 0.1% of 10-1, the resulting concentration after neutralization is 1.0 x 10-4M. Using the formula pH = -log [H+], we can calculate the new pH.
pH = -log [1.0 x 10-4]
pH = -(-4.00) = 4.00
Thus, the pH value after neutralizing 99.9% of the acid with a starting pH of 1 is approximately 4.00, which is significantly less acidic than the original solution. It does not reach 6.7, as that would suggest a far greater dilution or neutralization level.