Cheng's answer to Clara's Junior College 1 H2 Maths Singapore question.

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Cheng
Cheng's answer
237 answers (A Helpful Person)
1st
just minus the conc at 1 min with its initial conc.

Δ[A] = - 2.0 mol / dm3 min
Δ[B] = - 1.0 mol / dm3 min
Δ[C] = +1.0 mol / dm3 min

so C is correct