Question

What is the pH of a solution that has a [ ] = 0.020 M?

Answer 1

To calculate the pH of a solution with a [OH-] of 0.020 M, we use the formula [H3O+] = 10^-14/[OH-] to find the hydronium ion concentration and then -log[H3O+] to find the pH, which is approximately 12.3.

Step-by-step explanation:

The student is asking about calculating the pH of a solution with a given hydroxide ion concentration. Since pH and pOH are related, we can find the pH by first determining the hydronium ion concentration and then use the pH formula. First, the hydronium ion concentration is calculated using the formula: [H3O+] = 10-14/[OH-]. Assuming the missing substance meant in the question is OH-, with a concentration of 0.020 M, the hydronium ion concentration would be 10-14/0.020 M = 5.0 × 10-13 M. Then, the pH is found by taking the negative logarithm: pH = -log(5.0 × 10-13) which results in a pH of approximately 12.3, considering significant figures from the starting concentration.

Answer 2

HCl is a strong acid, it dissociates 100% (I.e. completely): [HCl]F = 0.020 M = [H3O+] So, pH = - log [H3O+] = -log [HCl]F = -log(. 020)=1.70 Voila!