Answer: The production of carbon dioxide is main characteristic of baking soda that makes it suitable for baking.
Baking soda gives carbon dioxide and water vapour on heating at even low temperature such as 100°C. The gas so formed turns lime water milky, which confirms the presence of carbon dioxide gas
.2NaHCO3 + Heat ⇨ Na2CO3 + CO2 + H2O
When Washing soda (Na2CO3) is heated it does not produce carbon dioxide even at high temperature, such as 200°C or 300°C. However sodium carbonate gives sodium oxide and carbon dioxide when heated at about 1000°C
Na2CO3.10H2O + Heat ⇨ Na2CO3 + 10H2O
The gas produced by heating of the samples can be checked by passing through lime water. If the lime water turns milky then the evolved gas is carbon dioxide and the heated substance is baking powder.