Answer to Question #56167 in Chemistry for Yehan

Question

1.Sally and Dave are both trying to chemically smother small fires. They forgot their decomposition reactions, but they both have sodium carbonate and sodium chlorate on hand. Sally dumps some sodium carbonate on her fire, and Dave dumps some sodium chlorate on his fire. One person succeeds in putting out his/ her fire, and the other person needs to go to the hospital to be treated for burns. Who succeeded and who got burnt? Explain your answer (with words and full sentences), and write any balanced chemical reactions that would help you justify your claims

Answer 1

The general explanation of the burning process is a reaction with an oxygen, which is presented in the air. To put out the fire, you have to prevent the access of the oxygen or air in general. And on the other hand, to increase the intensity of the fire you have to provide even more oxygen or heat.
Let's look into the chemical behaviour of these two compounds. Sodium carbonate in general is a heat resistant chemical, but at elevated temperatures it's possible to decompose it. The reaction is
Na₂CO₃(s)=Na₂O(s)+CO₂(g)
So even if the decomposition occurred, formed CO₂ (which is inert gas) immediately stops the burning. And if the reaction has not occurred, Sodium carbonate just covered the fire, to prevent oxygen, and also stops fire.
In the case of Sodium chlorate, it can easily decompose by following reaction :
2NaClO₃(s)=2NaCl(s)+3O₂(g)
In this case, oxygen has been produced, which can even increase the power of the fire, to cause burns.
Because Sally dumped Sodium carbonate, she succeed to put out the fire, and Dave got burnt, because he decomposed Sodium chlorate and liberated oxygen