5.1 Define the term rate of a reaction - NSC Physical Sciences - Question 5 - 2021 - Paper 2
Question 5
5.1 Define the term rate of a reaction.
5.2 Using the experimental setup above, state the measurements that must be made to determine the rate of this reaction.
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Worked Solution & Example Answer:5.1 Define the term rate of a reaction - NSC Physical Sciences - Question 5 - 2021 - Paper 2
Step 1
Define the term rate of a reaction.
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Answer
The rate of a reaction refers to the change in concentration of reactants or products per unit time. It can be expressed quantitatively as the amount of substance that reacts or is produced in a given time interval, denoted by the formula:
ext{Rate} = -rac{d[ ext{Reactants}]}{dt} ext{ or } rac{d[ ext{Products}]}{dt}
Step 2
Using the experimental setup above, state the measurements that must be made to determine the rate of this reaction.
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Answer
To determine the rate of the reaction, it is essential to measure the volume of CO₂ gas produced at regular time intervals. This can involve using a gas syringe to capture and quantify the volume of CO₂ generated during the reaction.
Step 3
Use the collision theory to explain how the average reaction rate in Experiment I differs from the average reaction rate in Experiment II.
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According to collision theory, the reaction rate is influenced by the frequency and effectiveness of collisions between reactant molecules. In Experiment I, a higher concentration of HCl (1.5 mol·dm⁻³) leads to more frequent collisions between reactive particles compared to Experiment II (2 mol·dm⁻³). This results in a higher average reaction rate for Experiment I, as more effective collisions occur per unit time due to the greater number of acid particles present.
Step 4
The average rate of the reaction in Experiment I during the first 2.5 minutes is 4.4 × 10⁻³ mol·min⁻¹.
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Answer
To find the average rate of reaction, we can use the formula:
ext{Average rate} = rac{n}{ ext{Δ}t}
Here,
n = total moles reacted in 2.5 minutes
extΔt=2.5extmin
Substituting the values, we have:
ext{Average rate} = rac{4.4 imes 10^{-3}}{2.5}
Step 5
Calculate the number of moles of At₂(CO₃)₃ that remains in the flask after 2.5 minutes.
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Answer
Using the average reaction rate previously calculated, we can determine the change in moles:
extΔn=extAveragerateimesextΔt=4.4imes10−3extmol⋅min−1imes2.5extmin=1.1imes10−2extmol
The initial amount of At₂(CO₃)₃ is 0.016 mol, so the remaining moles after the reaction is:
extRemainingmoles=0.016−0.011=0.005extmol
Step 6
Calculate the maximum volume of CO₂(g) that can be prepared at 25 °C in Experiment I.
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Answer
Using stoichiometry, we know that 1 mole of At₂(CO₃)₃ yields 3 moles of CO₂. Given that 0.005 moles of At₂(CO₃)₃ remain:
extMolesofCO2produced=0.011extmolimes3=0.033extmol
At 25 °C and standard atmospheric conditions, the molar volume of gas is 24,000 cm³, so:
extVolumeofCO2=0.033extmolimes24000extcm3/extmol=792cm3