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Question Video: Determining the Suitability of Experimental Apparatus for a Calorimetry Experiment Chemistry

The diagram below shows the experimental setup for a simple calorimeter to measure the enthalpy change in certain reactions. For which type of reaction would this experimental apparatus not be suitable for measuring the change in enthalpy? [A] Dissolution [B] Combustion [C] Displacement [D] Neutralization [E] Precipitation

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Video Transcript

The diagram below shows the experimental setup for a simple calorimeter to measure the enthalpy change in certain reactions. For which type of reaction would this experimental apparatus not be suitable for measuring the change in enthalpy? (A) Dissolution, (B) combustion, (C) displacement, (D) neutralization, or (E) precipitation.

A calorimeter is a device used for measuring energy transferred as heat during physical or chemical changes. It can be considered an isolated system where an isolated system is a system that does not allow for the transfer of matter or energy with its surroundings. Now that we know what this setup is used for, let’s look at the options from (A) to (E) to see which of these reaction types this experimental apparatus would not be suitable for. Option (A) is dissolution. Dissolution occurs when a solute dissolves in a liquid solvent. From the diagram, the reaction mixture appears to be a liquid. As the solution involves a liquid solvent, this apparatus would be suitable for dissolution.

Since the question asks “For which type of reaction would this experimental apparatus not be suitable?” option (A) is not the answer to this question. Option (B) is combustion. Combustion is burning. It involves reaction with oxygen. Combustion reactions require heat. But the polystyrene cup in this setup is not a very good conductor of heat, and combustion requires a supply of oxygen. But since the polystyrene cup has a lid on it, the oxygen supply would be limited. So, combustion is unlikely to occur, but if it did, it would produce a flame. But the polystyrene cup and cotton wool are flammable, so this experimental apparatus would not be suitable for combustion. Therefore, it seems like option (B) combustion is the correct answer to this question. But to confirm, let’s look at options (C) to (E).

Option (C) is displacement, which is where a more reactive species displaces the less reactive species from its compound. An example of this type of reaction would be magnesium powder displacing copper in an aqueous copper sulfate solution. Although displacement reactions can occur between solid reactants, they usually take place in water, so this apparatus is suitable for displacement. Thus, option (C) displacement is not the answer to this question.

Option (D) is neutralization. Neutralization involves an acid reacting with a base to produce a salt and water. The acid and base are usually dissolved in water. In this case, the basic solution may be referred to as an alkali, as an alkali is a soluble base. As in neutralization the reaction mixture is a liquid, the experimental apparatus is suitable, so option (D) is not the answer to this question.

Option (E) is precipitation. Precipitation reactions involve the formation of an insoluble product from the combination of solutions. In these reactions, the solvent is usually water, so this apparatus is suitable for precipitation. Thus, option (E) precipitation is not the answer to this question. Therefore, the answer to the question “For which type of reaction would this experimental apparatus not be suitable for measuring the change in enthalpy?” is (B) combustion.

It should be noted that although this simple calorimeter is not suitable for measuring the change in enthalpy for combustion, a constant volume calorimeter or a combustion calorimeter would be suitable.

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