Question

How does a mixture of aluminum powder and caustic soda help in clearing clogged drain pipes? Write a balanced chemical reaction to explain how this works.

Answer 1

The reaction of aluminum powder with caustic soda:

1. Aluminum is an amphoteric metal and when it reacts with caustic soda (Sodium hydroxide), it forms Sodium metaluminate $\left(NaAl{O}_2\right)$ and Hydrogen gas $\left(H_2\right)$ is evolved as a result of the reaction.
2. During the reaction, a large amount of heat is evolved because the reaction is exothermic.
3. The mixture of Aluminum powder $\left(Al\right)$ and Caustic soda $\left(NaOH\right)$ is commonly used as a drain cleaner because the reaction release hydrogen gas along with a large amount of heat which reacts with the oils and greases of the clog.
4. It helps to break down waste present in the clog and therefore, it helps in clearing the clogged drain.

The complete balanced reaction:

$\underset{(Aluminiumpowder)}{\underbrace{2Al\left(s\right)}}+\underset{(Sodiumhydroxide)}{\underbrace{2NaOH\left(aq\right)}}+\underset{\left(Water\right)}{\underbrace{2H_{2}O\left(l\right)}}\to \underset{(Sodiummetaluminate)}{\underbrace{2NaAl{O}_2\left(aq\right)}}+\underset{(Hydrogengas)}{\underbrace{3H_2\left(g\right)}}$