Convert the following pH value to concentration of H3O+: 1.20 (Keep 2 sig figs in your answer.)

Question

Convert the following pH value to concentration of H₃O⁺: 1.20 (Keep 2 sig figs in your answer.)

I did anti log^ -1.20 and got 0.630957344 as my concentration but im not sure how to put it into the correct sigfigs.

Answer 1

pH = -log[H3O+]

1.20 = -log[H3O+]

[H3O+] = 10^(-pH)

[H3O+] = 10^(-1.20)

[H3O+] = 0.0631 M (rounded to 2 sig figs)

Answer 2

pH = - log [H₃O¹⁺]

[H₃O¹⁺] = 10^-1.20 =0.06309... (not 0.6309...)

The question says to keep 2 sig figs in the answer, so it would be 0.063. The zero after the decimal point doesn't count as a sig fig.