The pHs are, respectively: 1.36, 1.35, 1.34. As we can see, when we change the second significant digit in the concentration, the pH value only changes the number in the second decimal place. This will happen due to the properties of the log 10 function. Therefore, it is important to use the significant figures of pH in this way, so we do not round the value too much.
Work Step by Step
We find: $$pH = -log[H_3O^+] = -log( 0.044 ) = 1.36 $$ $$pH = -log[H_3O^+] = -log( 0.045 ) = 1.35 $$ $$pH = -log[H_3O^+] = -log( 0.046 ) = 1.34 $$