Question

calculate relative molecular mass for Water and hydrogen chlorine

Answer 1

molecular mass of water = 18
since relative molecular mass=average mass of one molecule
                                                 ------------------------------------------
                                               1/12 of mass of one carbon 12 atom
relative molecular mass of water= 18/12 = 3/2=1.5
i hope that helps

Answer 2

Molar mass for water is

H2=2
O=16
therefore molar mass is 2+16=18
relative molar mass is 18/12=1.5

Hydrogen chloride is
H=1
cl=35.5
molar mass of HCl is 1+35.5 =36.5
relative molar mass is 36.5/12=3.41
hope it helps