Question Video: Identifying Which Unit Is Not Commonly Used to Measure a Rate of Reaction | Nagwa Question Video: Identifying Which Unit Is Not Commonly Used to Measure a Rate of Reaction | Nagwa

# Question Video: Identifying Which Unit Is Not Commonly Used to Measure a Rate of Reaction Science • Third Year of Preparatory School

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Which of the following is not a common unit used when measuring the rate of a chemical reaction? [A] L/min [B] g/s [C] mol/min [D] m/s [E] cm³/s

03:13

### Video Transcript

Which of the following is not a common unit used when measuring the rate of a chemical reaction? (A) Liters per minute, (B) grams per second, (C) moles per minute, (D) meters per second, or (E) cubic centimeters per second.

Chemical reactions take place at different speeds. Some reactions, such as explosions, happen very quickly. Other reactions, such as rusting, happen over a long period of time. As a reaction takes place, reactants form products. The concentration of the reactants decreases, and the concentration of the products increases. This describes the rate of a reaction, which is defined as the change in concentration of a reactant or product per unit of time.

The question is asking us, “Which of the given units is not commonly used when measuring the rate of a reaction?” To measure the rate of a reaction, we need a unit that can be used to measure the quantity of a substance per unit of time. Looking at the five answer choices, all of our options are either per minute or per second, which are all suitable units with which to measure time. We will have to look at the first part of these units to identify which unit would not be suitable for measuring the amount of a substance and thus the correct answer.

Let’s start with answer choice (A) liters per minute. Liters can measure a volume of substance produced or consumed in a reaction. Since this unit would measure a change in volume of substance per minute, it is a suitable unit to measure the rate of a reaction. And so it is not the answer to this question.

Answer choice (B), grams per second, and (C), moles per minute, feature units which measure amount of matter. Changes to amounts of matter measured in grams per second or moles per minute are conceivable units to measure rates. So these answer choices can be eliminated.

Answer choice (E), cubic centimeters per second, measures a change in volume per second, which could be measured with an apparatus, such as a gas syringe. Since this unit would measure a change in volume of a substance per unit of time and could thus be used to measure the rate of a reaction, it can be eliminated.

This leaves us with answer choice (D) meters per second. A meter is a unit of measurement for a length. So meters per second would measure the change in a distance over time. This unit would not be commonly used to measure changes in reactants or products in a chemical reaction and so would not be a useful unit to measure reaction rates. Answer choice (D) is the correct answer.

Therefore, the unit that is not a common unit used when measuring a rate of a chemical reaction is answer choice (D) meters per second.

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