Photo AI
In aqueous solution, 2-chloro-2-methylpropane, (CH₃)₃CCl, reacts with sodium hydroxide, NaOH - CIE - A-Level Chemistry - Question 4 - 2015 - Paper 1
Question 4
In aqueous solution, 2-chloro-2-methylpropane, (CH₃)₃CCl, reacts with sodium hydroxide, NaOH. This is a nucleophilic substitution reaction. (CH₃)₃CCl(aq) + NaOH(aq)... show full transcript
Worked Solution & Example Answer:In aqueous solution, 2-chloro-2-methylpropane, (CH₃)₃CCl, reacts with sodium hydroxide, NaOH - CIE - A-Level Chemistry - Question 4 - 2015 - Paper 1
Step 1
Step 2
Calculate the half-life for this reaction. Show all your working and show clearly any construction lines on the graph.
Answer
To find the half-life from the graph, locate the point where the concentration of (CH₃)₃CCl is half of its initial value. For example, if the initial concentration is 0.6 mol/dm³, the half-life would be the time it takes for the concentration to fall to 0.3 mol/dm³. From the graph, this occurs between 49-53 seconds. Hence, the half-life is approximately between 49 to 53 seconds.
Step 3
What would be the effect on the half-life of this reaction if the initial concentration of (CH₃)₃CCl was doubled?
Answer
Doubling the initial concentration of (CH₃)₃CCl would typically lead to a decrease in the half-life for a first-order reaction, since the rate of reaction depends on the concentration of the reactant. The specific effect would depend on the order of the reaction, but for a first-order reaction, the half-life remains constant regardless of concentration.
Step 4
Use the graph in (b) to determine the rate of reaction at 80s. Show all your working.
Answer
At 80 seconds, using the graph, find the corresponding concentration of (CH₃)₃CCl. Suppose it is 0.42 mol/dm³. Using the rate equation:
rate = k[(CH₃)₃CCl] = k[0.42]
Substituting the values for k would be necessary for the final rate determination.
Step 5
Calculate the value of the rate constant, k, for this reaction and give its units.
Answer
To determine k, use the rate equation:
rate = k[(CH₃)₃CCl]. Assuming we found the rate from the previous answer to be 0.00263 mol/dm³/s at a concentration of 0.42 mol/dm³:
0.00263 = k[0.42]
This gives:
k = 0.00263 / 0.42 = 0.00626. The units for k in this context would be dm³/mol·s.