Question

Which is the valid observation for the reaction...? `3O_2(g)rarr2O_3(g)`

`"1. The mass of the products increase."`
`"2. This is an exothermic reaction."`
`"3. The pressure of the reaction mixture should DECREASE."`
`"4. The pressure of the reaction mixture should INCREASE."`

Answer 1

`"Option 3"` is the best answer.

Explanation:

All chemical reactions conserve mass. If you start with 10 g of reactant, from all sources, at MOST, you can get 10 g of reactant. In practice, you are not even going to get that.

The equation clearly shows that the number of gaseous molecules is reduced; nevertheless, mass is conserved:

`3O_2(g) rarr 2O_3(g)`

And thus pressure is reduced due to the decrease in the number of gaseous particles.

`"Option 3"` certainly describes the scenario.