Agniveer Army Chemical Reactions

A chemical reaction involves breaking old bonds and forming new bonds. The atoms remain the same, but their arrangement changes. For example, when iron rusts, iron atoms combine with oxygen atoms to form iron oxide

Mass is conserved - total mass of reactants equals total mass of products (Law of Conservation of Mass) 2. Atoms are neither created nor destroyed, only rearranged 3. Energy changes always occur - reactions either release heat (exothermic) or absorb heat (endothermic) 4. Chemical equations must be balanced

Start with the most complex molecule first. Balance metals, then non-metals, then hydrogen and oxygen last. Use the 'LCM method' - find LCM of atoms appearing on both sides

When identifying precipitation reactions, remember that most carbonates, sulfides, and hydroxides are insoluble except those of Group 1 metals and ammonium. This helps predict which combinations will form precipitates. For energy changes, remember: Combustion and respiration are always exothermic. Photosynthesis and electrolysis are always endothermic. This pattern appears frequently in RRB papers.