1In the reaction \( 4\mathrm{Fe} + 3\mathrm{O_2} \rightarrow 2\mathrm{Fe_2O_3} \), what are the reactants and the products?
2In the same equation, how many atoms are there in the reactants and in the products?
3What else can be learned from a balanced chemical equation?
4State the law of conservation of mass. How does it explain why chemical equations must be balanced?
5Why must a subscript never be changed while balancing? Give an example.
6Balance \( \mathrm{Al} + \mathrm{N_2} \rightarrow \mathrm{AlN} \) by the hit and trial method.
7Balance \( \mathrm{H_2O_2} \rightarrow \mathrm{H_2O} + \mathrm{O_2} \).
8How many sodium atoms and oxygen atoms are there in \( 2\mathrm{Na_2O} \)?
9What does the sign \( \Delta \) written over the arrow mean? Give one example.