1 Marks Question

Question 11 Mark

In a reaction, $2A \rightarrow$ Products, the concentration of A decreases from $0.5 \ \ce{mol L^{–1}}$ to $0.4 \ \ce{mol L^{–1}}$ in $10$ minutes. Calculate the rate during this interval?

Answer

$\text{Average Rate}=\frac{-1}{2}\frac{\triangle\ [\text{A}]}{\triangle\ \text{t}}$
$=\frac{-1}{2}\frac{\text{[A]}_2-\text{[A]}}{\text{t}_2-\text{t}_1}$
$=\frac{-1}{2}\frac{(0.4-0.5)}{10}$
$=\frac{-1}{2}\frac{(-0.1)}{10}$
$= 5 \times 10^{-3} \ce{M min^{-1}}$

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Question 21 Mark

For a reaction, $A + B \rightarrow$ Product; the rate law is given by, $r = k [ A]^{1/2} [B]^2.$ What is the order of the reaction?

Answer

The order of the reaction is sum of the powers on concentration.
So that sum will.
$r = k [A]^{1/2}[B]^2$
Order of reaction $= 12 + 2 = 2.5.12 + 2 = 2.5.$

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Question 31 Mark

For the reaction $R \rightarrow P$, the concentration of a reactant changes from $0.03M$ to $0.02M$ in $25$ minutes. Calculate the average rate of reaction using units of time both in minutes and seconds.

Answer

Average rate of reaction
$=-\frac{\triangle[\text{R}]}{\triangle\text{t}}$
$=-\frac{[\text{R}]_2-[\text{R}]_1}{\text{t}_2-\text{t}_1}$
$=-\frac{0.02-0.03}{25}\text{M mim}^{-1}$
$=-\frac{-0.01}{25}\text{M mim}^{-1}$
$= 4 \times 10^{-4} M min^{-1}$
$=\frac{4\times10^{-4}}{60}\text{M s}^{-1}$
$= 6.67 \times 10^{-6} Ms^{-1}$

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Question 41 Mark

Define 'order of a reaction'.

Answer

The sum of powers of the concentration terms of the reactants in the rate law expression is called the order of that chemical reaction.
Alternate answer
rate $= k[A]^P [B]^q$
Order of reaction $= P+q.$

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Question 51 Mark

Write the rate equation for the reaction $2\text{A + B}\xrightarrow{\ \ \ \ \ \ }\text{C}$ if the order of the reaction is zero.

Answer

Rate $= k[A]^0[B]^0$ or Rate $= k.$

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Question 61 Mark

Why is it that instantaneous rate of reaction does not change when a part of the reacting solution is taken out?

Answer

Instantaneous rate is measured over a very small interval of time, hence, it does not change when a part of solution is taken out.

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Question 71 Mark