I just need help with #5 :))

Enough of a monoprotic weak acid is dissolved in water to produce a 0.0172 m solution. if the ph of the resulting solution is 2.39 at 20 °c, determine the pka for the acid.

What does earth’s rotation on its axis cause? the tides night and day passing of years phases of the moon

11. phosphorus-32 is radioactive and has a half life of 14 days. how much of a 124 mg sample of phosphorus-32 is present after 56 days? a) 7.75 mg b) 15.5 mg c) 31.0 mg d) 62.0 mg