The question is: The pH of lemon juice at 298 K is found to be 2.32. What is the concentration of H3O (+) ions in the solution. So, you just have to use the formula pH = log { 1 / [H3O+] } = - log { [H3O+] }, from which you can solve for [H3O+] as: [H3O+] = 10 ^ (- pH) = 10 ^ (-2.32) = 0.00479 M = 4.79 * 10^ -3 Answer: 4.79 * 1 0^-3M