Tag: chemistry

Questions Related to chemistry

Consider following compounds:


$I: K _4[Fe(CN) _6], II:NH _4Cl, III: H _2SO _4$ 

Ionic, covalent and coordinate bonds are present in :

chemistry chemical bond and chemical equation coordinate bond types of bonds and properties chemical bonding and structure

  1. I, II and III

  2. I and III

  3. II and III

  4. I and II

Show answer
Correct Option: A
Explanation:

$H _{2}SO _{4}$  has $3$ types of bonds- ionic, covalent and coordinate. Sulphur is the central atom,surrounded by $4$ oxygen atoms and $2$ hydrogen atoms places on left of any $2$ oxygen atoms. Now, oxygen shares one electron each with the sulphur and hydrogen atom. But by this only $2$ oxygen atoms will be able to complete octet. The remaining $2$ will complete by coordinate bonding. Both the oxygen atoms will take electrons from sulphur but sulphur won't take theirs ie sharing from only one end. This is called coordinate bond. Hydronium ions are attached with sulphate ions using ionic bonding
${ K } _{ 4 }[{ Fe(CN) } _{ 6 }]\ $: has ionic bond between ${ K }^{ + }and  { [{ Fe(CN) } _{ 6 }] }^{ 4- }$, coordinate bonding in $CN$ and covalent bond in ${ [{ Fe(CN) } _{ 6 }] }^{ 4- }$
$\ { NH } _{ 4 }Cl\ $: has ionic bond between $\ { { NH } _{ 4 } }^{ + }and  { Cl }^{ -}$, coordinate bonding in $\ { { NH } _{ 4 } }^{ + }$ and covalent bond in $\ { { NH } _{ 3 } .}^{  }\quad \$

Which of the following contains a coordinate covalent bond ?

chemistry chemical bonding and structure coordinate bond types of bonds and properties chemical bond and chemical equation

  1. $N _2H^{+} _{5}$

  2. $BaCl _2$

  3. $HCl$

  4. $H _2O$

Show answer
Correct Option: A
Explanation:

${ N } _{ 2 }{ H } _{ 5 }^{ + }$ is formed from ${ N } _{ 2 }{ H } _{ 4 }$ which has a lone pair of electrons on $'N'$ and positive charge on $'H'$ takes away its electron and to complete duplet, a co-ordinate bond is present from $N$ to $H$.

$H _4N _2 + H^+ \rightarrow[H _4N _2\to H]^+$

Which of the following molecule has dative bond?

chemistry chemical bonding and structure coordinate bond types of bonds and properties chemical bond and chemical equation

  1. CO

  2. $CO _3^{2-}$

  3. $SO _4^{-2}$

  4. All of these

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Correct Option: A

The time required to complete $\dfrac{3}{4}th$ of first order reaction is $32 min.$ then find $t _{\frac{1}{2}} = ?$

chemistry chemical kinetics kinetic study of some first order reactions rate of chemical reaction endothermic and exothermic reactions

  1. $16$

  2. $160$

  3. $1600$

  4. $32$

Show answer
Correct Option: A
Explanation:

$t _{\dfrac{3}{4}} = 2t _{\dfrac{1}{2}} = 32min.$
$t _{\dfrac{1}{2}} = 16min.$

The first order rate constant for dissociation of $N _2O _5$ is $6.2\times 10^{-4}s^{-1}$. The half-life period (in $s$) of this dissociation will be.

chemistry chemical kinetics kinetic study of some first order reactions rate of chemical reaction endothermic and exothermic reactions

  1. $1117.7$

  2. $111.7$

  3. $223.4$

  4. $160.9$

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Correct Option: A
Explanation:
$t _{1/2}=\displaystyle\frac{0.693}{k}$
$=\displaystyle\frac{0.693}{6.2\times 10^{-4}}=1117.7s$

For a first order reaction with half-life of $150$ second , the time taken for the concentration of the reactant to fall from $M/10$ to $M/100$ will be approximately 

chemistry chemical kinetics kinetic study of some first order reactions rate of chemical reaction endothermic and exothermic reactions

  1. $1500\ s$

  2. $500\ s$

  3. $900\ s$

  4. $600\ s$

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Correct Option: A

How many minutes will it take to plate out $5.0g$ of $Cr$ form a $Cr _2(SO _4) _3$ solution using a current of $1.50A$?

chemistry chemical kinetics kinetic study of some first order reactions rate of chemical reaction endothermic and exothermic reactions

  1. $254$

  2. $309$

  3. $152$

  4. $103$

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Correct Option: B

Which of the following is first order ?
i) Decomposition of $NH _{4}NO _{3}$ in aqueous solution.
ii) Inversion of cane sugar in the presence of an acid
iii) Base hydrolysis of ethyl acetate.
iv) All radioactive decays.
The correct combination is:

chemistry chemical kinetics kinetic study of some first order reactions rate of chemical reaction endothermic and exothermic reactions

  1. i, ii, iv

  2. All are correct

  3. ii, iv

  4. ii, iii, iv

Show answer
Correct Option: A
Explanation:

Base hydrolysis of ethyl acetate is a second order reaction.
The other reactions are first order reactions.

The acid hydrolysis of the ester is:
(i) first order reaction
(ii) bimolecular reaction
(iii) unimolecular reaction
(iv) second order reaction

The true statements are:

chemistry chemical kinetics kinetic study of some first order reactions rate of chemical reaction endothermic and exothermic reactions

  1. i, ii

  2. All are correct

  3. ii, iv

  4. ii, iii, iv

Show answer
Correct Option: A
Explanation:

$CH _{3}COOC _{2}H _{5}+H _{2}O\rightarrow CH _{3}COOH+C _{2}H _{5}OH$
$ rate=K[CH _{3}COO\ C _{2}H _{5}]^{1}[H _{2}O]^{0}$
thus, it is first order & bi molecular reaction.

Thus, statement i and ii are correct.

The hydrolysis of acetic anhydride$(CH _3CO) _2O+ H _2O\rightarrow2CH _3COOH$ is an example of :

chemistry chemical kinetics kinetic study of some first order reactions rate of chemical reaction endothermic and exothermic reactions

  1. Pseudo first order reaction

  2. Pseudo second order reaction

  3. Zero order reaction

  4. Third order reaction

Show answer
Correct Option: A
Explanation:

It is an example of pseudo first order reaction because here $H _{2}O$ is in excess. Thus, rate of reaction depends on only concentration of acetic anhydride.
So, rate is given by
$=k[(CH _{3}CO) _{2}O]$