Final answer:
To find the pH of the new HCl solution after dilution, use the dilution equation to calculate the new concentration and then the pH formula. The calculation shows that the pH of the diluted solution is approximately 1.70.
Step-by-step explanation:
When you start with 150 ml of 0.1 M HCl solution and take 100 ml from it to add to 400 ml of distilled water, you are diluting the solution.
The dilution equation, M1V1 = M2V2, is used to find the new concentration (M2) after dilution.
The initial molarity (M1) is 0.1 M, and the initial volume (V1) is 100 ml.
The final volume (V2) after adding 400 ml of water is 500 ml. Therefore, M2 = (M1V1) / V2 = (0.1 M * 100 ml) / 500 ml = 0.02 M.
Next, to find the pH of the new solution, we use the fact that HCl is a strong acid and completely dissociates in water.
This means that the concentration of hydronium ions, [H3O+], is equal to the molarity of the HCl solution.
pH is calculated using the formula pH = -log[H3O+]. Given that M2 is 0.02 M, the pH is -log(0.02), which simplifies to approximately 1.70.