Statement I correctly describes the effect of adding manganese dioxide (MnO₂) to potassium chlorate (KClO₃) when heated. MnO₂ acts as a catalyst, speeding up the decomposition of KClO₃ into potassium chloride (KCl) and oxygen gas (O₂). The reaction is 2KClO₃ (s) → 2KCl (s) + 3O₂ (g). Statement II claims that manganese dioxide acts as a negative catalyst. A negative catalyst (or inhibitor) slows down a reaction. Since MnO₂ increases the rate of decomposition of KClO₃, it is a positive catalyst.
Statement-I: Oxygen gas is easily produced at a faster rate by heating a mixture of potassium chlorate and manganese dioxide than heating potassium chlorate alone. Statement-II: Manganese dioxide acts as a negative catalyst.
Asked in UPSC NDA 1 2015 · Topic: Inorganic Chemistry (Catalysis by Inorganic Compounds)
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Answer: C. Statement I is true but Statement II is false
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