2A + B gives 3C + D. Which of the following does not express the reaction rate?
Correct answer: D. -1/3 d[C]/dt
- A. -d[B]/dt
- B. d[D]/dt
- C. -1/2 d[A]/dt
- D. -1/3 d[C]/dt
Explanation
Rate is expressed as the change in concentration divided by the coefficient, with a minus sign for reactants because they are being consumed and a plus sign for products because they are being formed. C is a product, so its term must be positive, and writing it with a minus sign makes the expression wrong. The other three all give the same positive rate.
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About Rate of Reaction
Reaction rate measures the change in concentration of a reactant or product per unit time. Questions connect rate with concentration, temperature, pressure, surface area, catalysts and nature of reactants, and may involve rate laws, reaction order, activation energy and collision theory. Rate describes speed, whereas equilibrium describes the final balance of opposing reactions.
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