Question Video: Recognizing Why Warm Hydrochloric Acid Has a Faster Rate of Reaction with Magnesium than Cold Hydrochloric Acid | Nagwa Question Video: Recognizing Why Warm Hydrochloric Acid Has a Faster Rate of Reaction with Magnesium than Cold Hydrochloric Acid | Nagwa

Question Video: Recognizing Why Warm Hydrochloric Acid Has a Faster Rate of Reaction with Magnesium than Cold Hydrochloric Acid Chemistry • Third Year of Secondary School

The reaction between warm hydrochloric acid and magnesium has a faster rate of reaction than the reaction between cold hydrochloric acid and magnesium. Which statement explains this observation?

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Video Transcript

The reaction between warm hydrochloric acid and magnesium has a faster rate of reaction than the reaction between cold hydrochloric acid and magnesium. Which statement explains this observation? (A) The particles are more concentrated and have a greater mass. (B) The particles are moving faster and have a greater surface area. (C) The particles are moving faster and have a greater mass. (D) The particles are more concentrated and have greater energy. Or (E) the particles are moving faster and with greater energy.

The rate of a chemical reaction is the rate at which reactants are converted into products. We can think of this as the speed of a chemical reaction. We are told in the question that two reactions between hydrochloric acid and magnesium are carried out. We are also told that the reaction using warm hydrochloric acid has a faster rate of reaction than the reaction using cold hydrochloric acid. We need to determine which statement explains this observation.

We can use collision theory to help us. Collision theory states that reactions only happen when particles collide with sufficient energy and the correct orientation. According to this theory, if the collision frequency or the energy of the collisions increase, then the rate of reaction will increase. As the difference between the two reactions is the temperature of the hydrochloric acid, we should consider how temperature might affect the collision frequency or energy of the collisions.

We may recall that the speed of a particle depends on temperature. At cold temperatures, particles move about relatively slowly. As the temperature increases, the particles gain kinetic energy and move faster. This means that at higher temperatures, the particles collide more often and with more energy. Thus, increasing the temperature will increase the rate of reaction.

So we now know that the reaction between warm hydrochloric acid and magnesium has a faster rate of reaction than the reaction between cold hydrochloric acid and magnesium because the particles are moving faster and with greater energy, answer choice (E).

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