The given reaction is rewritten below,
2NaHCO3 + 85kJ --> Na2CO3 + H2O + CO2
It can be concluded that every 2 moles of NaHCO3 one needs 85kJ of energy. To determine the amount of energy needed for 3 moles of NaHCO3, the concept of ratio and proportion may be used.
(85 kJ/ 2moles NaHCO3) (3 moles NaHCO3)
= 127.5 kJ
Answer: 127.5 kJ