Question

plss answer these two points?

Answer 1

a) formula of carbon dioxide is CO2 
so no. of atoms in compound =no. of atoms in carbon + no. of atoms in oxygen molecules
= 44 u

Answer 2

carbon and oxygen combine with ratio of 3 : 8 by mass

e.g 3part of mass of carbon combine with 8 part of mass of oxygen

but we know,
atomic mass of carbon = 12 g/mol
atomic mass of oxygen= 16 g/mol
so,
C : O = 12/3 : 16/2 = 2 : 1

by cross method

so, formula of compound = CO2

2)
a) in nature oxygen is required for living thing . so, generally in that time all know about oxygen . so, I think oxygen is used
b) atom mass = atomic mass of oxygen/{16× 6.023 × 10^23 } is not accurate but nearly to accurate. no any metal in that time give this type of correction .