Types of Chemical Reaction — Important Questions

C₃H₈ + 5O₂ → 3CO₂ + 4H₂O + Heat

Step 1: In combustion reactions, a fuel reacts rapidly with oxygen to form oxides and release heat energy. Step 2: Propane (C₃H₈) is a hydrocarbon present in LPG gas used for cooking. Step 3: When propane burns completely, carbon atoms form CO₂ and hydrogen atoms form H₂O. Step 4: Balancing the equation: C₃H₈ + 5O₂ → 3CO₂ + 4H₂O + Heat. Step 5: The other options show incomplete or incorrect reactions — Option A produces C₃H₆ (wrong product), Option C shows decomposition not combustion, and Option D is a steam reforming reaction.

A double arrow with heads pointing in opposite directions (⇌)

Step 1: In a reversible reaction, the products can be converted back to the reactants. Step 2: This means the reaction proceeds in BOTH forward and backward directions simultaneously. Step 3: To show this two-way nature, a special double arrow (⇌) is used, with one arrowhead pointing to the right (forward reaction) and one pointing to the left (backward reaction). Step 4: A single arrow (→) is used for irreversible reactions that proceed only in one direction. Step 5: The other arrow types are not standard chemistry notation for reversible reactions.

The rate of forward reaction equals the rate of backward reaction.

Step 1: Chemical equilibrium is attained in a reversible reaction when no net change occurs in the amounts of reactants and products. Step 2: At equilibrium, both forward and backward reactions are still occurring — they have NOT stopped. Step 3: The key condition for equilibrium is: Rate of forward reaction = Rate of backward reaction. Step 4: Because both reactions are happening at equal rates, the concentrations of reactants and products remain constant. Step 5: This is called dynamic equilibrium — it appears static from outside but both reactions are continuously occurring.

Colour of the reaction vessel

Step 1: The rate of a chemical reaction depends on several physical and chemical factors that affect how often reacting particles collide. Step 2: Temperature increases reaction rate because more heat energy means more energetic particles that break bonds faster. Step 3: Concentration of reactants affects rate because more particles per volume means more frequent collisions. Step 4: A catalyst increases reaction rate by providing an alternative pathway for the reaction without being consumed. Step 5: The colour of the reaction vessel has absolutely no chemical or physical effect on the reactio