Explain qno.79 Ans(3):

79. The pressure of CO₂ at 27^oC for the reaction CaCO_​3(S) $\rightleftharpoons$CaO(s) + CO₂(g) is 10 atm. If the number of moles of CO₂ is doubled keeping volume and temperature constant. The pressure of CO₂ will become .
(1) 20 atm
(2) 15 atm
(3) Remain same
(4) Data insufficient.