100 mL mixture of CO and CO₂ is mixed with 30 mL of oxygen and sparked in a eudiometer tube. The residual gas after treatment with aqueous KOH has a volume of 10 mL which remains unchanged when treated with alkaline pyrogallol solution. If all the volumes are measured under  same conditions, identify the correct statement(s).

$2\mathrm{CO}+{\mathrm{O}}_2\to 2{\mathrm{CO}}_2$ . The residual gas is CO.

Volume of CO oxidised = 2 × 30 = 60mL;
Volume of CO = 60 + 10 = 70 mL
hence the volume of CO remains
unreacted = 70 - 60 = 10 mL

Volume of CO₂, initially present in the mixture = 100 - 70 = 30mL
Volume of CO₂, formed = 60 mL; Volume of CO₂
absorbed by KOH = 30 + 60 = 90 mL
As per reaction O₂ is completely consumed.