The reaction of zinc and EXCESS dilute hydrochloric acid is used to investigate factors that affect reaction rate - NSC Physical Sciences - Question 5 - 2018 - Paper 2
Question 5
The reaction of zinc and EXCESS dilute hydrochloric acid is used to investigate factors that affect reaction rate. The balanced equation for the reaction is:
$$Zn(s... show full transcript
Worked Solution & Example Answer:The reaction of zinc and EXCESS dilute hydrochloric acid is used to investigate factors that affect reaction rate - NSC Physical Sciences - Question 5 - 2018 - Paper 2
Step 1
Experiment 1 and experiment 5 are compared. Write down the independent variable.
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Answer
The independent variable is the concentration of hydrochloric acid (HCl) used in each experiment. In this case, the concentration varies between 2.0 mol·dm−3 for Experiment 1 and 2.0 mol·dm−3 for Experiment 5, but it is emphasized that the other factors were kept constant.
Step 2
Define reaction rate.
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Reaction rate refers to the change in concentration of reactants or products per unit time. It can be defined mathematically as:
Rate=ΔtΔ[extProducts]
This indicates how quickly reactants are converted to products over a specified time interval.
Step 3
Write down the value of k in experiment 4.
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In experiment 4, the value of k is 14 min.
Step 4
5.4.1 Experiment 3
Give a reason for the answer.
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Answer
Graph B represents Experiment 3 as it shows the highest concentration of HCl which reflects a higher number of effective collisions between reactant molecules, thereby increasing the reaction rate.
Step 5
5.4.2 Experiment 5
Give a reason for the answer.
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Graph C represents Experiment 5 as it corresponds to the highest temperature that provides sufficient kinetic energy for the reacting particles, leading to an increase in the rate of reaction.
Step 6
5.5.1 What is the function of the catalyst in this experiment?
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The catalyst speeds up the reaction by providing an alternative pathway with a lower activation energy, thus increasing the rate of reaction without being consumed in the process.
Step 7
5.5.2 How will the heat of reaction in experiment 6 compare to that in experiment 1? Choose from: GREATER THAN, EQUAL TO or LESS THAN.
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The heat of reaction in experiment 6 will be LESS THAN that in experiment 1 due to the presence of the catalyst which reduces the activation energy required for the reaction to proceed.
Step 8
5.6 Calculate the average rate of the reaction (in mol·min$^{-1}$) with respect to zinc for experiment 2 if 1.5g of zinc is used.
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Answer
To find the average rate of the reaction, we first need to calculate the number of moles of zinc used. Given the molar mass of zinc is approximately 65 g/mol:
n(Zn)=65 g/mol1.5 g=0.023 mol
The reaction time for experiment 2 is 12 minutes. Thus, the average rate can be calculated as:
