The activation energy for the reaction no2(g)+co2(g)⟶no(g)+co(g) is ea = 300 kj/mol and the change in enthalpy for the reaction is δh = -100 kj/mol . what is the activation energy for the reverse reaction?

The correct answer is 400 KJ/mol.  

The given reaction:  

NO₂ (g) + CO₂ (g) ⇒ NO (g) + CO₂ (g)

The activation energy or Ea for the reaction is 300 KJ/mol.  

The change in enthalpy for the reaction is, ΔH = -100 KJ/mol, this is for forward reaction, for backward or reverse reaction, ΔH = 100 KJ/mol

The Ea for reverse reaction is calculated by using the formula,  

Ea (forward) + ΔH

= 300 + (+100)

= 400 KJ/mol

Therefore, the activation energy for the reverse reaction is 400 KJ/mol

atomic number of carbon is 6

electronic configuration of carbon is 1s²2s²2p²

orbital diagram of carbon is as shown here in the image.

"record the time to complete a chemical reaction" would most likely be part of a lab procedure.