What mass of

Moles of O₂=wt of O₂/mol.wt of O₂

=20/32

=.625 moles of O₂ 

and the number of moles of O₂ will be equal to the number of moles of CO₂ as they contain same number of atoms as are with O₂.

hence, number of moles of CO₂ =.625

and we know that,

Number of moles=wt./mol.wt

molecular wt of CO₂=12+2*16=44

.625=wt of CO2/44

wt of CO2=27.5 g.