The above reaction is slow at the start but speeds up after some time. This is because of:2.41 (s) + NaOH (aq) + 2H2O ------- 2NaAlO2 + 3H2
Correct answer: C. The protective oxide layer of the aluminum dissolves and the meal surface is exposed to the reactant
- A. The reaction is exothermic and the heat generated speeds up the reaction
- B. The hydrogen liberated during the reaction acts as a catalyst
- C. The protective oxide layer of the aluminum dissolves and the meal surface is exposed to the reactant
- D. Sodium aluminate is highly soluble; therefore, it helps the reaction move in the forward direction
Explanation
Aluminium has a protective coat, due to which it initially reacts slowly. After a while, this coat dissolves, causing the reaction to speed up due to the increased exposed surface area of aluminum. The generation of heat increases the temperature. So if the reaction was exothermic, an increase in temperature would cause the reaction to move in a backward direction. A catalyst cannot be consumed or produced in a reaction, and hydrogen gas is being produced here, so it cannot be a catalyst. Solubility is not related to the speed of reaction.
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About Factors Affecting Rate of Reaction
Reaction rate depends on the nature and concentration of reactants, pressure for gases, temperature, surface area and catalysts. Collision theory explains these effects through collision frequency, orientation and activation energy, while questions often distinguish a catalyst's effect on reaction rate from its lack of effect on equilibrium composition.
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