Respuesta :

The answer is:  [C]:  "4" .
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Note:  To balance this equation, the coefficient, "4", should be placed in front of the PCl₃ ;  and the coefficient, "6", should be placed in front of the Cl₂ .
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The balanced equation is:
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             P₄ (s) + 6 Cl₂ (g)  → 4 PCl₃ (l)   .
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