Tag: rates of reaction

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Questions Related to rates of reaction

Multiple choice chemistry rates of reaction introduction to rate of reaction rate of chemical reaction rate of reaction

For a chemical reaction, $A \rightarrow products$, the rate of reaction doubles when the concentration of A is increased by a factor of 4, the order of reaction is :

  1. 2

  2. 0.5

  3. 4

  4. 1
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
let x be order of reaction and K be rate of constant.
* A$\rightarrow $ products.
$ \cfrac { K\cfrac { { \left( A \right)  }^{ x } }{ time }  }{ K\cfrac { { \left( 4A \right)  }^{ x } }{ time }  } or,\quad \cfrac { 1 }{ 2 } = { \left( \cfrac { A }{ 4A }  \right)  }^{ x }\\ or,\quad \cfrac { 1 }{ 2 } ={ \left( \cfrac { 1 }{ 4 }  \right)  }^{ x }$      (reciprocating)
$\\ or,\quad 2={ \left( 4 \right)  }^{ x }\\ or,\quad 2={ { 2 }^{ 2 } }^{ x }\\ or,\quad 2x=1\\ or,\quad x=\cfrac { 1 }{ 2 } \\ x=0.5$
Multiple choice chemistry rates of reaction introduction to rate of reaction rate of chemical reaction rate of reaction

The term $-\dfrac{dc}{dt}$ in a rate equation refers to:

  1. the concentration of a reactant

  2. the decrease in concentration of the reactant with time

  3. the velocity constant of reaction

  4. none of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The term $-\dfrac{dc}{dt}$ in a rate expression indicates the decrease in concentration of the reactant with time. It is the minus sign which is used to show the decrease in concentration of the reactant.

Multiple choice chemistry rates of reaction introduction to rate of reaction rate of chemical reaction rate of reaction

For a first order reaction, A$\rightarrow$ products, the concentration of A changes from $0.1$M to $0.025$ M $80$ minutes. The rate of reaction when the concentration of A is $0.01$M, is:

  1. $1.73\times 10^{-5}$M/min
  2. $3.47\times 10^{-4}$M/min
  3. $3.47\times 10^{-5}$M/min
  4. $1.73\times 10^{-4}$M/min
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

K$= \frac { 2.303 }{ t } \log { \left[ \dfrac { { A } _{ 0 } }{ A }  \right]  } $


$\quad =\dfrac { 2.303 }{ 80 } \log [{ \dfrac { 0.1 }{ 0.025 }  }]$

$k= 0.0173\quad { min }^{ -1 }$

$\therefore $ Rate$= K\left[ A \right]$

$\quad \quad \quad =0.0173\left[ 0.01 \right]$

$\quad \quad \quad = 1 .73 \times { 10 }^{ -4 } $

$\quad \quad \quad =1.73\times{ 10 }^{ -4 }M/min$

Hence, the correct option is $(D)$

Multiple choice chemistry rates of reaction introduction to rate of reaction rate of chemical reaction rate of reaction

Which of the following is (are) true for first order reaction?

  1. Rate of reaction is fastest at the beginning of reaction.

  2. Rate of reaction is fastest when (reactants)=(products)

  3. Rate of reaction increases with temperature

  4. Ea decreases considerably as temperature as temperature increases, hence the reaction becomes faster
Reveal answer Fill a bubble to check yourself
A,C Correct answer
Explanation

A] True. for first order reactions, products are formed at the fastest rate during the  beginning of the reaction.

B] False. When reactants>Products, the rate of reaction is fast.
C] True. Increasing the temperature increases the rate of reaction.
D] False. Activating energy does not decrease, but increasing the temperature allows crossing of energy barrier.

Multiple choice chemistry rates of reaction introduction to rate of reaction rate of chemical reaction rate of reaction

For the reaction $2A + B + C \rightarrow 2D$. The observed rate law is Rate=$K[A]{ [B] }^{ 2 }$. Correct statements are
a) An increase of cone .of C does not affect the rate
b)Doubling the conc of A doubles the rate
c)Tripling the conc of B increases the rate by 9 times
d)Doubling the conc of C, doubling the rate

  1. a,b,c

  2. b,c,d

  3. d

  4. c,d
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Given  rate is $k[A]{ [B] }^{ 2 }$

 It is overall ${ 3 }^{ rd }$ order  reaction with a following  first order  and B following second order.
 (a) True  C is not affecting the rate of reaction.
 (b) True $rate _{ 1 }\quad =k[A]{ [B] }^{ 2 }\ rate _{ 2 }\quad =k[2A]{ [B] }^{ 2 }=2k[A]{ [B] }^{ 2 }\ =2\times rate _{ 1 }$
 (c) True $rate _{ 1 }\quad =k[A]{ [B] }^{ 2 }\ rate _{ 3 }=k[A]{ [3B] }^{ 2 }=9Kk[A]{ [B] }^{ 2 }\ =9\times rate _{ 1 }$
(d)False C does not affected  the rate in any manner.

Multiple choice chemistry rates of reaction introduction to rate of reaction rate of chemical reaction rate of reaction

${ SO } _{ 2 }$ react with ${ O } _{ 2 }$ as follows :


 ${ 2SO } _{ 2 }+{ O } _{ 2 }\rightarrow { 2SO } _{ 3}$ 


The rate of disappearance of ${ SO } _{ 2 }$ is $2.4\times { 10 }^{ -4 }$ mol ${ lit }^{ -1 }{ min}^{ -1 }$, then :

  1. Rate of reaction is $1.2\times { 10 }^{ -4 }\quad mole{ lit }^{ -1\quad }{ min }^{ -1 }$
  2. Rate of appearance of ${ SO } _{ 3 }$ is $2.4\times { 10 }^{ -4 } { mole\quad lit }^{ -1 }min^{ -1 }$
  3. Rate of disappearance of ${ O } _{ 2 }$ is $1.2\times { 10 }^{ -4 } { mole\quad lit }^{ -1 }min^{ -1 }$
  4. Rate of reaction is twice the rate of disappearance of ${ SO } _{ 2 }$
Reveal answer Fill a bubble to check yourself
B,C,D Correct answer
Multiple choice chemistry rates of reaction introduction to rate of reaction rate of chemical reaction rate of reaction

Which of the fallowing can enhance the rate of the reaction ?

  1. increasing the temperature

  2. increasing the concentration of products

  3. increasing the activation energy

  4. using a +Ve catalyst
Reveal answer Fill a bubble to check yourself
A,D Correct answer
Explanation

Solution:- (A) increasing the temperature and (D) using a +ve catalyst
  • Temperature is a measure of the kinetic energy of a system, so higher temperature implies higher average kinetic energy of molecules and more collisions per unit time. Hence an increase in temperature is accompanied by an increase in the reaction rate. 
  • A higher concentration of reactants leads to more effective collisions per unit time, which leads to an increased reaction rate (except for zero order reactions). Similarly, a higher concentration of products tends to be associated with a lower reaction rate.
  • Catalysts (e.g., enzymes) lower the activation energy of a chemical reaction and increase the rate of a chemical reaction without being consumed in the process. 
  • Hence, using a positive catalyst and increasing the temperature, both can enhance the rate of reaction.

Multiple choice chemistry rates of reaction introduction to rate of reaction rate of chemical reaction rate of reaction

Rate of formation of $SO _{3}$ according to the reaction $2SO _{2}+O _{2} \rightarrow 2SO _{3}$ is $1.6 \times 10^{-3}\ kg\ min^{-1}$ Hence rate at which $SO _{2}$ reacts is :-

  1. $1.6 \times 10^{-3}\ kg\ min^{-1}$
  2. $8.0 \times 10^{-4}\ kg\ min^{-1}$
  3. $3.2 \times 10^{-3}\ kg\ min^{-1}$
  4. $1.28\times 10^{-3}\ kg\ min^{-1}$
Reveal answer Fill a bubble to check yourself
B Correct answer