Q1. Minimum molecular mass
There must be at least one atom of #"Na"# in methyl orange (MeO).
∴ The minimum molecular mass (MMM) is
#"MMM" = 1 color(red)(cancel(color(black)("atom Na"))) × (22.99 color(red)(cancel(color(black)("u Na"))))/(1 color(red)(cancel(color(black)("atom Na")))) × "100 u MeO"/(7 color(red)(cancel(color(black)("u Na")))) = "330 u MeO"#
Q2. Atoms of #"N"# and #"S"#.
#"Mass of N" = 330 color(red)(cancel(color(black)("u MeO"))) × "12.8 u N"/(100 color(red)(cancel(color(black)("u MeO")))) = "42 u N"#
#"Atoms of N" = 42 color(red)(cancel(color(black)("u"))) × "1 atom N"/(14.01 color(red)(cancel(color(black)("u")))) = "3 atoms N"#
#"Mass of S" = 330 color(red)(cancel(color(black)("u MeO"))) × "9.8 u S"/(100 color(red)(cancel(color(black)("u MeO")))) = "32 u S"#
#"Atoms of S" = 32 color(red)(cancel(color(black)("u"))) × "1 atom S"/(32.06 color(red)(cancel(color(black)("u")))) = "1 atom S"#
