Answer
a)
Oxygen: $15.873\ u'$
Avogadro's Number $N'=5.9803\times10^{23}\ molecules/mol$
b)
Hydrogen: $1.00798\ u'$
Avogadro's Number $N'=6.0278\times10^{23}\ molecules/mol$
Work Step by Step
a) For this standard $1.00794\ u = 1.0000\ u'$
Oxygen: $15.9994\ u \times 1.0000\ u'/1.00794\ u=15.873\ u'$
Carbon: $12.011\ u \times 1.0000\ u'/1.00794\ u=11.916\ u'$
Avogadro's Number $N'=(11.916/12.000)\times6.022\times10^{23}=5.9803\times10^{23}\ molecules/mol$
b) For this standard $15.9994\ u = 16.0000\ u'$
Hydrogen: $1.00794\ u \times 16.0000\ u'/15.9994\ u=1.00798\ u'$
Carbon: $12.011\ u \times 16.0000\ u'/15.9994\ u=12.011\ u'$
Avogadro's Number $N'=(12.011/12.000)\times6.022\times10^{23}=6.0278\times10^{23}\ molecules/mol$
