Potassium chlorate (KClO3) decomposes to form potassium chloride (KCl) and pure oxygen (O2) gas as shown below.

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What amount of KClO3 is required to supply 28.0 L of oxygen gas at STP? (The molar mass of KClO3 is 122.55 g/mol.)
A. 102 g
B. 102.12 g
C. 306.36 g
D. 306.4 g