What is bigger 30 dm or 3 m?
30dm = 300cm = 3m. They're the same.
The volume of a typical bacterial cell is on the order of 1.0 micrometers cubed. At pH 7.0 how many hydrogen ions are contained inside a bacterial cell?
pH=-log10[H+]=7 so [H+]=10^-7M molar concentration (M) = number of moles / dm^3 so number of moles of H+=10^-7 mol/dm^3 * volume in dm^3 1 dm^3 = (0.1m)^3 = 10^-3 m^3 1 um^3 = (10^-6 m)^3 = 10^-18 m^3 so volume in dm^3 = 10^-15 dm^3 therefore the number of moles of H+=10^-22 there are 6.022*10^23 molecules per mole so there are about 60 H+ ions in the bacterial cell at pH 7