2480.6 kJ required.
For:
#CH_(4(g))+2O_(2(g))rarrCO_(2(g))+2H_2O_((l))#
#DeltaH_(comb)=-882.0"kJ"#
So for the reverse reaction:
#CO_(2(g))+2H_2O_((l))rarrCH_(4(g))+2O_(2(g))#
#DeltaH=+882.0"kJ"#
#[M_r]CH_4=16.0#
So #16.0"g"# requires #882.0"kJ"#
So #1"g"rarr882.0/16.0"kJ"#
So #45"g"rarr(882.0)/(16.0)xx45=2480.0"kJ"#