Tag: chemistry

Questions Related to chemistry

If the rate with respect to $O _2, NO, NO _2$ are $\displaystyle \frac{- \Delta [O _2]}{\Delta t}$ $= \dfrac{-1}{2}\dfrac{\Delta [NO]}{\Delta t}$, $= \dfrac{+1}{2} \dfrac{\Delta [NO _2]}{\Delta t}$, then the corresponding chemical equation is $2NO+O _2  \rightarrow NO _2$.
chemistry chemical kinetics introduction to chemical kinetics understanding chemical kinetics rate of chemical reaction

  1. True

  2. False

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Correct Option: B

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

chemistry chemical kinetics introduction to chemical kinetics understanding chemical kinetics rate of chemical reaction

  1. $1.6\times { 10 }^{ -3 }kg\quad { min }^{ -1 }$

  2. $8.0\times { 10 }^{ -4 }kg\quad { min }^{ -1 }$

  3. $3.2\times { 10 }^{ -3 }kg\quad { min }^{ -1 }$

  4. $1.28\times { 10 }^{ -3 }kg\quad { min }^{ -1 }$

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Correct Option: D
Explanation:

$2 SO _2 + O _2 \rightleftharpoons  2 SO _3$


$\dfrac{1}{2}\dfrac{d[SO _3]}{dt} = 1.6 \times 10^{-3} kg/min = \dfrac{1.6 \times 10^{-3}}{80} mol/min$                             $[\because M _{SO _3}= 80 \times 10^{-3} Kg/mol]$


$\dfrac{-1}{2}\dfrac{d[SO _2]}{dt} = \dfrac{+1}{2}\dfrac{d[SO _3]}{dt}$

$= -\dfrac{1.6 \times 10^{-3}}{80 \times 10} $ mol/min

$= -\dfrac{1}{50} \times 64 \times 10^{-3} = -1.28 \times 10^{-3} $ kg/min

For a reaction
$2A+B\rightarrow C+D$, the active mass of $B$ is kept constant but that of $A$ is tripled. The rate of reaction will -

chemistry chemical kinetics introduction to chemical kinetics understanding chemical kinetics rate of chemical reaction

  1. Decrease by $3$ times

  2. Increased by $9$ times

  3. Increase by $3$ times

  4. Unpredictable

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Correct Option: B
Explanation:

According to the given reaction, $ Rate = k[A]^{2}[B]^{1} $

When A becomes 3A i.e. triples, the rate will become: $ Rate^{'} = k[3A]^{2}[B]^{1} = 9k[A]^{2}[B] $
Thus, rate of reaction is increased by 9 times. 

The study of chemical kinetics becomes highly complicate if there occurs:

chemistry chemical kinetics introduction to chemical kinetics understanding chemical kinetics rate of chemical reaction

  1. reversible reaction

  2. side reaction

  3. surface reaction

  4. none of these

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Correct Option: B,C
Explanation:

The study of chemical kinetics becomes highly complicate if there occurs side reactions or surface reactions.These reactions bring changes in the value of rate constant and not help to proceeds the reaction in the right manner.

The container of $2$ litrer contains $4$ mole of $N _{2}O _{5}$. On heating to $100^{\circ}C, N _{2}O _{5}$ undergoes complete dissociation to $NO _{2}$ and $O _{2}$. Select the correct answers if rate constant for decomposition of $N _{2}O _{5}$ is $6.2\times 10^{-4}sec^{-1}$.
1. The mole ratio before and after dissociation is $4 : 2$
2. Half life of $N _{2}O _{5}$ is $1117\ sec$ and it is independent of concentration.
3. Time required to complete $40$% of reaction is $824\ sec$.
4. If volume of container is doubled, the initial rate of decomposition becomes half of the initial rate.

chemistry chemical kinetics introduction to chemical kinetics understanding chemical kinetics rate of chemical reaction

  1. $1, 3, 4$

  2. $1, 2, 3, 4$

  3. $3, 4$

  4. $2, 3, 4$

Show answer
Correct Option: C
Explanation:

Because reaction is first order

$\vartheta =k[A]$
$A=A _{0}e^{-kt}$

for which

$t _{40}=824$sec
if$v _{f}=2V _{i}\Rightarrow C _{f}=\frac{C _{i}}{2}\Rightarrow \vartheta _{f}=\frac{\vartheta _{i}}{2}$

Ozone hole means :

chemistry air around us importance of oxygen is air present everywhere around us? air as a natural resource

  1. thinning of the ozone layer

  2. a large sized hole in ozone layer

  3. small hole scattered in the ozone layer

  4. thickening of ozone in ozone layer

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Correct Option: A
Explanation:

"Ozone hole" means thinning of the ozone layer.


The ozone hole is not technically a “hole” where no ozone is present but is actually a region of exceptionally depleted ozone layer.

Hence the option A is correct.

Choose the correct answer form the alternatives given.
Scuba divers are at high risk due to high concentration of dissolved gases while breathing air at high pressure under water. The tanks used by Scuba divers are filled with :-

chemistry air around us importance of oxygen is air present everywhere around us? air as a natural resource

  1. Air diluted with helium

  2. 02

  3. N

  4. A mixture of nitrogen and helium

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Correct Option: A

The nitrogen molecules present in the air can be converted into nitrates and nitrites by :

chemistry air around us importance of oxygen is air present everywhere around us? air as a natural resource

  1. nitrogen fixation

  2. carbon fixation

  3. industries in the form of by ctprodu

  4. cereal plants

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Correct Option: A
Explanation:

The nitrogen molecules present in the air can be converted into nitrates and nitrites by nitrogen fixation.


Hence the option A is correct.

Reformation of ozone in stratosphere is powered by :

chemistry air around us importance of oxygen is air present everywhere around us? air as a natural resource

  1. atmospheric oxygen

  2. UV radiation

  3. sunlight

  4. heat

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Correct Option: B
Explanation:

Reformation of ozone in stratosphere is powered by UV radiation.

The part of atmosphere which contains constant gases with known composition called :

chemistry air around us importance of oxygen is air present everywhere around us? air as a natural resource

  1. Homosphere

  2. Thermosphere

  3. Heterosphere

  4. None of these

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Correct Option: A
Explanation:

The part of the atmosphere which contains constant gases with a known composition called homo-sphere.

The homosphere is the lower of the two and the location in which turbulent mixing dominates the molecular diffusion of gases. In this region, which occurs below 100 km (about 60 miles) or so, the composition of the atmosphere tends to be independent of height.