The force holding ions together in an ionic crystal is: MCQ with Answer and Explanation

Explanation:
Catalysts provide an alternative pathway with lower activation energy, increasing reaction rate without being consumed. They do not affect equilibrium constant or thermodynamic parameters (ΔH, ΔS). They can be solid (heterogeneous), liquid, or gas. Enzymes are liquid-phase catalysts. A catalyst does not change the position of equilibrium, only speeds up attainment.

Explanation:
Autocatalysis occurs when one of the products of a chemical reaction acts as a catalyst for that same reaction. As the reaction proceeds and the product accumulates, the rate of the reaction increases. A classic example is the oxidation of oxalic acid by potassium permanganate, where the Mn2+ ions produced catalyze the reaction.

Explanation:
Hydrochloric acid (HCl) is commonly used for pickling (cleaning) steel to remove rust and scale (iron oxides) before further processing like galvanizing or plating. Reaction: Fe₂O₃ + 6HCl → 2FeCl₃ + 3H₂O. Sulfuric acid is also used. Nitric acid is an oxidizer and would passivate some metals. Acetic acid is too weak.