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9. (a) Explain (i) activation energy, (ii) effective collision - Leaving Cert Chemistry - Question 9 - 2009
Question 9
9. (a) Explain (i) activation energy, (ii) effective collision. The effect of temperature on the rate of a chemical reaction was investigated using dilute solutions... show full transcript
Worked Solution & Example Answer:9. (a) Explain (i) activation energy, (ii) effective collision - Leaving Cert Chemistry - Question 9 - 2009
Step 1
Explain (i) activation energy
Answer
Activation energy is defined as the minimum energy required for colliding particles (molecules) to react. It refers to the energy threshold that must be surpassed for a chemical reaction to occur, enabling the reactants to reach the transition state. Higher activation energy means that fewer molecules will have sufficient energy to undergo the reaction.
Step 2
Explain (ii) effective collision
Answer
An effective collision occurs when colliding particles possess not only sufficient energy but also the correct orientation to react with each other. Such collisions result in the formation of products. A collision is deemed effective if it leads to the formation of a chemical bond or a product, maximizing the chances of reaction.
Step 3
Describe how the timer for the reaction between the solutions of hydrochloric acid and sodium thiosulfate was obtained at room temperature.
Answer
To measure the time for the reaction, one would mix equal volumes of hydrochloric acid and sodium thiosulfate in a conical flask placed over a marked paper. Upon mixing the solutions, the flask is started, and the timer is activated. The reaction produces sulfur, which gradually becomes opaque. The reaction time is recorded from the moment of mixing until the marked paper beneath the flask is no longer visible.
Step 4
In a reaction mixture what effect, if any, does an increase in temperature of 10 K have on each of the following:
Answer
i) The number of collisions: An increase in temperature generally results in an increase in kinetic energy for the particles, leading to more frequent collisions between them.
ii) The effectiveness of the collisions: A rise in temperature enhances the energy of collisions, increasing the likelihood of effective collisions where reactants interact correctly.
iii) The activation energy: The activation energy itself does not change with temperature; however, increasing temperature allows more particles to have enough energy to overcome this activation energy threshold.
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Step 8
Explain how this catalyst affects the reaction and the platinum catalyst speeds up the oxidation of the hot methanol.
Answer
The platinum catalyst lowers the activation energy required for the oxidation of methanol. By providing an alternative reaction pathway with a lower energy barrier, it enhances the reaction rate and allows the reaction to proceed at a faster rate, thereby efficiently converting methanol (CH3OH) into product gases.
Step 9
Explain how a catalyst poison interferes with this type of catalyst.
Answer
A catalyst poison interferes with the catalytic process by binding to the active sites on the catalyst, blocking access to the reactants. This significantly reduces the catalyst's effectiveness and can halt the reaction entirely by preventing it from occurring on the catalyst surface.
Step 10
Give another example of a reaction which involves the same type of catalyst, indicating clearly the reactants(s) and the catalyst.
Answer
An example of another reaction using a platinum catalyst is the oxidation of ethylene (C2H4) to ethylene oxide (C2H4O). In this reaction, the reactants are ethylene and oxygen, while platinum serves as the catalyst facilitating the reaction.