Tag: chemistry

Questions Related to chemistry

Soap solution is colloidal in nature and remove the dust particles by which of the following process?

chemistry adsorption and colloids applications of colloids colloids around us the colloidal state

  1. Emulsification

  2. Adsorbtion

  3. Stripping

  4. Distillation

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Correct Option: A,B
Explanation:

Soap solution removes dust particles through emulsification and absorption of them.

Silver iodide is used for producing artificial rains because $AgI$:

chemistry adsorption and colloids applications of colloids colloids around us the colloidal state

  1. is easy to spray at high altitude

  2. is insoluble in water

  3. is easy to synthesize

  4. has crystals similar to ice

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Correct Option: D
Explanation:

Solid silver iodide is preferred as a nucleator for artificially stimulated rain because its crystal lattice parameters are close to those of ice, and for that reason are more effective than other salts in causing small ice crystals in clouds to melt.

To stop bleeding from an injury ferric chloride can be applied
Which comment about the statement is justified?

chemistry adsorption and colloids applications of colloids colloids around us the colloidal state

  1. It is not true, ferric chloride is a poison

  2. It is true, ${Fe}^{3+}$ ions coagulate blood which is negatively charged sol

  3. It is not true, ${Cl}^{-}$ ions from positively charged sol, profuse bleeding takes place

  4. It is true, coagulation takes place because of formation of negatively charged sol with ${Cl}^{-}$ ions.

  5. It is not true, ferric chloride is ionic and gets into blood stream

Show answer
Correct Option: B
Explanation:

To stop bleeding from an injury, Ferric chloride can be applied because of the following reason:

(A) $Fe^{3+}$ ions coagulate blood which is a negatively charged solution
(B) $Cl^−$ ions coagulate blood which is a positively charged solution

Blood being a colloidal solution, its coagulation by Hardy-Shuze's law states " Higher the charge on cation higher will be its efficiency to coagulate the colloidal solution" . Thus Option B is correct.

An atom of each element has a definite combining capacity called : 

chemistry structure of the atom electronic configuration and valency electron configuration periodic trends in physical properties

  1. valency

  2. affinity

  3. bonding

  4. energy levels

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Correct Option: A
Explanation:

An atom of each element has a definite combining capacity called its valency.

For example Na has electronic configuration 2,8,1 
So, valency is 1 as after losing one electron it will have stable octet.

The electrons present in the outermost shell of an atom are known as :

chemistry structure of the atom electronic configuration and valency electron configuration periodic trends in physical properties

  1. protons

  2. neutrons

  3. octet

  4. valence electrons

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Correct Option: D
Explanation:

The electrons present in the outermost shell of an atom are known as valence electrons.

The valency of nitrogen in nitrogen dioxide is:

chemistry structure of the atom electronic configuration and valency electron configuration periodic trends in physical properties

  1. 1

  2. 2

  3. 3

  4. 4

Show answer
Correct Option: D
Explanation:

$(D)$  $ 4$


$Sol. $  let the valency of nitrogen in be $ x$. 
           valency of oxygen = $ -2 $
          For $NO _2 $ it will be ,
                                $ x + 2 \times(-2) = 0 $
                                 $ x = +4 $
Hence, the valency of nitrogen in $ NO _2$ is $ +4 $. 

Valency of magnesium and oxygen in $MgO$ is:

chemistry structure of the atom electronic configuration and valency electron configuration periodic trends in physical properties

  1. one and one

  2. two and two

  3. one and two

  4. two and one

Show answer
Correct Option: B
Explanation:

Ans. $(B)$ $(two$ $and$ $two)$

This is because magnesium loses two electrons to have an octet and oxygen gains two electrons to have an octet. The final formula of magnesium oxide is ${MgO}$. So, the valencies magnesium and oxygen in $ {MgO}$ are $2$ and $2$ .

Valence electrons are responsible for the chemical properties of an atom.

chemistry what is inside atom electronic configuration and valency electron configuration periodic trends in physical properties

  1. True

  2. False

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Correct Option: A

The element with the highest first ionisation potential is:

chemistry periodic table electronic configuration and valency electron configuration periodic trends in physical properties

  1. Boron

  2. Carbon

  3. Nitrogen

  4. Oxygen

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Correct Option: C

The ionisation potential of hydrogen atom is $13.6\ eV$. The energy of required to remove an electrons in the $n=2$ state of hydrogen atom is:

chemistry periodic table electronic configuration and valency electron configuration periodic trends in physical properties

  1. $27.2\ eV$

  2. $13.6\ eV$

  3. $6.8\ eV$

  4. $3.4\ eV$

Show answer
Correct Option: D
Explanation:
$E _n=-13.6\ ev\left (\dfrac {Z^2}{n^2}\right)=\dfrac {-E _1}{n^2}[I.E _1 =-E _1 =13.6\ eV \Rightarrow E _1=-13.6\ eV]$

$\therefore E _2 =\dfrac {-13.6\ ev}{4}=-3.4ev$

$\therefore I.E _2=-E _2 =3.4\ ev$.

Option D is correct.