To find the pH of a bleach solution, we need to use the relationship between the concentrations of hydronium ions and hydroxide ions in water:
pH + pOH = 14
where pH is the negative logarithm of the hydronium ion concentration [H3O+], and pOH is the negative logarithm of the hydroxide ion concentration [OH-]. Since we are given the concentration of hydroxide ions, we can find pOH:
pOH = -log[OH-]
pOH = -log(1.9×10^-5)
pOH = 4.72
Now we can use the relationship between pH and pOH to find the pH of the bleach solution:
pH + pOH = 14
pH = 14 - pOH
pH = 14 - 4.72
pH = 9.28
Therefore, the pH of the bleach solution is approximately 9.28.