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Balance the decomposition of potassium chlorate: KClO$_3$ $\xrightarrow{\Delta}$ KCl + O$_2$. The correct coefficients (KClO$_3$, KCl, O$_2$) are:
A1, 1, 1
B1, 1, 3
C2, 2, 3
D2, 2, 1
Answer & Solution
Correct answer: C. 2, 2, 3
1. Oxygen appears as 3 atoms in one KClO$_3$ but as 2 atoms in O$_2$; the LCM of 3 and 2 is 6.
2. Put 2KClO$_3$ to get 6 O atoms on the left, and 3O$_2$ to get 6 O atoms on the right.
3. This makes 2 K and 2 Cl on the left, so place 2KCl on the right to match: 2KClO$_3$ $\longrightarrow$ 2KCl + 3O$_2$.
4. Check: K = 2, Cl = 2, O = 6 on both sides. The 1,1,1 and 1,1,3 sets leave O unequal, and 2,2,1 gives only 2 O on the right, so they are wrong.
_Source: Balbharati (Maharashtra Board) Class 10 Science & Technology, Ch 3 "Chemical Reactions and Equations", p.50_
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