Final answer:
When mixing equal volumes of two acidic solutions with pH values of 6 and 4, the resulting pH will be closer to 4 than 6 due to the logarithmic nature of the pH scale. The final pH can be precisely calculated using hydronium ion concentrations. The resulting pH will certainly not be 8 as it would not be possible from mixing two acidic solutions.
Step-by-step explanation:
The question about mixing equal volumes of solutions with different pH levels pertains to the concept of pH calculation in acid-base chemistry. When you mix equal volumes of a solution with pH 6 (slightly acidic) and another with pH 4 (more acidic), the resulting pH will not be the average of the two pH values because the pH scale is logarithmic. The pH of a neutral solution at 25 °C is 7, with solutions having a pH less than 7 being acidic and those with a pH greater than 7 being basic.
A solution with a pH of 4 has a hydronium ion concentration 100 times greater than a solution with a pH of 6, since a difference of one pH unit corresponds to a tenfold difference in hydrogen ion concentration. When the two solutions are mixed, the resulting pH will be closer to 4 than to 6, because the solution with pH 4 has a significantly higher concentration of hydrogen ions.
It's important to note that the final pH of the mixture can be calculated more accurately using the concentrations of hydronium ions, but it requires more information than just the pH values. The resulting pH will definitely not be 8, as the student mentioned, since this would indicate a basic solution, which can't result from mixing two acidic solutions.