Question 30

The hydrogen-ion concentration of a pH 4 solution is 100,000 times stronger than that of a pH 9 solution.

The difference in hydrogen-ion concentration between a pH 4 and a pH 9 solution is quantified by the pH scale, which is logarithmic. A decrease of 5 pH units (from 9 to 4) represents a 10^5 or 100,000 times increase in hydrogen-ion concentration.

A) 50

Option A is incorrect because a pH difference of 5 units cannot correspond to a mere 50 times increase. The logarithmic nature of the pH scale indicates that each unit represents a tenfold change in concentration.

B) 100,000

Option B is correct as it accurately reflects the logarithmic relationship between pH levels. A pH of 4 is indeed 100,000 times more acidic, or has 100,000 times greater hydrogen-ion concentration than a pH of 9.

C) 0.000001

Option C is incorrect because it suggests an extremely low concentration, which misrepresents the relationship between pH and hydrogen-ion concentration. The correct comparison yields a much larger value, not a fraction.

D) 5

Option D is incorrect since it implies that the difference in concentration is only 5 times, which significantly underestimates the actual difference. The logarithmic scale indicates a much greater disparity between the two pH values.

Conclusion

The correct answer is B) 100,000, as it accurately describes the hydrogen-ion concentration difference between pH 4 and pH 9 solutions. All other options fail to represent the logarithmic nature of pH, which indicates that a change of 5 pH units results in a concentration change of 100,000 times, not just a factor of 50, 5, or an inaccurate representation of concentration.