Answer:
Reference image attached
Explanation:
Please see the attached image.
4.88x10^20 H2O2 molecules
PH measures the concentration of hydrogen ions on the log 10 scale. Thus, a pH 5 solution has 2 order of magnitude difference from that of pure water, which has a pH of 7.
Therefore,

. A solution of pH 5 has 100 times more hydrogen ions that that of pure water.
Answer is 13.668! Or in scientific notation it would be .13668 x 10^2