Veriy by calculating that
a) 5 moles of `CO_(2)` and 5 moles of `H_(2)O` do not have the same mass.
b) 240 g of calcium and 240 g magnesium elements have a mole ratio of `3:5`

Explanation

a) Molar mass of `CO_(2)=12 + 2 xx 16 = 12+32=44g mol^(-1)`
`therefore` 1 mole of `CO_(2)` has mass = 44g
`therefore` 5 moles of `CO_(2)` have mass =`44 xx 5=220g`
Similarly, molar mass of `H_(2)O= 2xx1 + 16=18g mol^(-1)`
`therefore` 1 mole of `H_(2)O` has mass = 18g
`therefore` 5 moles of `H_(2)O` have mass = `18 xx 5=90g`
`therefore` Both the values are not same. So, it is verified.
b) molar mass of calcium =40g.
`therefore` 40 g of Ca has number of moles =`1/40 xx 240=6 mol`
Molar mass of magnesium =24g
`therefore` 24g of Mg has number of moles =1 mol
`therefore` 240 g of Mg has number of moles =`1/24 xx 240=10` mol
`("Number of moles of Ca")/("Number of moles of Mg") = 6/10=3/5`, So, it is verified.