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Define rate of reaction - Leaving Cert Chemistry - Question b - 2006
Question b
Define rate of reaction. The effect of concentration on reaction rate can be studied using the reaction between sodium thiosulfate solution and hydrochloric acid. T... show full transcript
Worked Solution & Example Answer:Define rate of reaction - Leaving Cert Chemistry - Question b - 2006
Step 1
Define rate of reaction.
Answer
Rate of reaction is defined as the change in the concentration of a reactant or product over time. This can be mathematically expressed as:
ext{Rate} = rac{ ext{Change in concentration}}{ ext{Time}}
This definition highlights how the concentration of either the reactants decreases or the products increases as the reaction progresses.
Step 2
Which product of the reaction causes the reaction mixture to become cloudy?
Answer
The product that causes the reaction mixture to become cloudy is sulfur (S). As the reaction between sodium thiosulfate and hydrochloric acid occurs, sulfur precipitates out of the solution, leading to cloudiness.
Step 3
If a higher concentration of sodium thiosulfate solution were used in the reaction, would the time taken for the cross to become invisible be greater, less or unchanged? Explain your answer.
Answer
The time taken for the cross to become invisible would be less. This is because reaction rate is proportional to the concentration of the reactants. A higher concentration of sodium thiosulfate increases the frequency of particle collisions, thus speeding up the reaction.
Step 4
If the conical flask were surrounded by ice-water, would the time taken for the cross to become invisible be greater, less or unchanged? Explain your answer.
Answer
The time taken for the cross to become invisible would be greater. Lower temperatures result in slower molecular movement, which decreases the frequency of collisions between reactant molecules, leading to a slower reaction rate.