Tag: chemistry

Questions Related to chemistry

When metal foundry products are cleaned by shot blasting, heat is generated by friction. Nitrogen is used for:

chemistry nitrogen and sulfur nitrogen gas component of air - nitrogen nitrogen

  1. providing an inert atmosphere

  2. cooling the blast chamber

  3. reducing friction

  4. displacing hot air

Show answer
Correct Option: A
Explanation:
Nitrogen commonly used as inert gas to create inert atmosphere because the strong triple bond needs a lot of energy to break and participate in a reaction. Hence, ${N} _{2}$ is referred as an inert gas.

Which of the following is not a nitrogenous fertilizer ?

chemistry nitrogen and sulfur nitrogen gas component of air - nitrogen nitrogen

  1. Calcium cyanamide

  2. CAN

  3. Super phosphate of lime

  4. Urea

Show answer
Correct Option: C
Explanation:
Calcium cyanamide ($CaCN _2$) is nitrogenous fertilizer.
CAN is calcium ammonium nitrate and urea $NH _2-CO-NH _2$ is also nitrogenous fertilizer.
Superphosphate of lime, $Ca(H _2PO _4) _2$ is fertilizer of phosphorous.So it's not the fertilizer of nitrogen.
Hence option C is correct.

In Kjeldahl's method, nitrogen present is estimated as:

chemistry nitrogen and sulfur nitrogen gas component of air - nitrogen nitrogen

  1. $N _2$

  2. $NH _2$

  3. $NO _2$

  4. none of these

Show answer
Correct Option: B
Explanation:

Kjeldahl method is a method that is used the quantitatuin estimation of nitrogen conlaining in inorganic substances like $NH _3/NH _4^+$, and in organic substances.In kjeldah's method, notrogen is estimated in following steps : 

$Step$ $1:$Degradation: Sample$+H _SO _4\longrightarrow {(NH _4)} _2SO _4+CO _2+SO _2+H _2O$
$Step$ $2:$ Ammonia is liberated : ${(NH _4)} _2SO _4+2NaOH\longrightarrow Na _2SO _4+2H _2O+2NH _3$
$Step$ $3:$ Ammonia is captured : $B{(OH)} _3+H _2O+NH _3\longrightarrow NH^+ _4+B{(OH)} _4^-$
$Step$ $4:$ Back titration : $B{(OH)} _3+H _2O+Na _2CO _3\longrightarrow NaHCO _3+NaB{(OH)} _4+CO _2+H _2O$
Thus in Kjeldahl's method, nitrogen present is estimated as $NH _2$.

In the reaction of $2NO+{ O } _{ 2 }\rightarrow 2{ NO } _{ 2 }$, if the rate of disappearance of ${ O } _{ 2 }$ is $16gm$ ${ min }^{ -1 }$, then the rate of apperance of ${ NO } _{ 2 }$ is:

chemistry nitrogen and sulfur nitrogen gas component of air - nitrogen nitrogen

  1. $90\ gm\ { min }^{ -1 }$

  2. $46\ gm\ { min }^{ -1 }$

  3. $28\ gm\ { min }^{ -1 }$

  4. $32\ gm\ { min }^{ -1 }$

Show answer
Correct Option: A
Explanation:
$2NO+{ O } _{ 2 }\rightarrow 2N{ O } _{ 2 }$
$-\cfrac { 1 }{ 2 } \cfrac { d\left[ NO \right]  }{ dt } =\cfrac { -d\left[ { O } _{ 2 } \right]  }{ dt } =\cfrac { 1 }{ 2 } \cfrac { d\left[ N{ O } _{ 2 } \right]  }{ dt } $
$\cfrac { -d\left[ { O } _{ 2 } \right]  }{ dt } =16ℊ{ min }^{ -1 }=\cfrac { 16 }{ 16 } mol{ min }^{ -1 }=1mol{ min }^{ -1 }$
$\cfrac { d\left[ N{ O } _{ 2 } \right]  }{ dt } =2\times \cfrac { -d\left[ { O } _{ 2 } \right]  }{ dt } =2\times 1=2mol/min$
No. of moles$=\cfrac { weight }{ mol.wt } $
$2\times $Mol. wt of $N{ O } _{ 2 }=$wt
$2\times 46=$ wt $\Rightarrow $Weight of $N{ O } _{ 2 }=92ℊ$
Rate of appearance of $N{ O } _{ 2 }=92ℊ/min\approx 90ℊ/min$
Therefore, option $A$ is correct.

If the constituents of a solid-liquid mixture have different masses, then we can separate them using:

chemistry separation of matter sedimentation, decantation and filtration other methods of separation separation methods

  1. sublimation

  2. centrifugation

  3. winnowing

  4. evaporation

Show answer
Correct Option: B
Explanation:

Centrifugation is a technique which involves the application of centrifugal force to separate particles from a solution. The larger the size and the larger the density of the particles, the faster they separate from the mixture. Example- washing machine works on the principle of centrifugation.

State a method to separate a solid-liquid mixture containing a soluble solid in the liquid components.

chemistry separation of matter sedimentation, decantation and filtration other methods of separation separation methods

  1. Fraction distillation

  2. Filtration

  3. Sedimentation

  4. Distillation

Show answer
Correct Option: D
Explanation:

A solid-liquid mixture containing a soluble solid in the liquid components can be separated by distillation.

Which method is used to separate salt from the salt water?

chemistry separation of matter sedimentation, decantation and filtration other methods of separation separation methods

  1. Filtration

  2. Distillation

  3. Evaporation

  4. Sedimentation

Show answer
Correct Option: C

Select the methods to separate a solid-liquid mixture containing an insoluble solid in the liquid components. 

chemistry separation of matter sedimentation, decantation and filtration other methods of separation separation methods

  1. Sedimentation

  2. Filtration

  3. Distillation

  4. Fractional distillation

Show answer
Correct Option: A,B

Which of the following can be used for Solid-Solid mixture separation?

chemistry separation of matter sedimentation, decantation and filtration other methods of separation separation methods

  1. Mechanical separation

  2. Magnetic separation

  3. Gravity separation

  4. All of above

Show answer
Correct Option: D

Water is said to be permanently hard when it contains:

chemistry separation of matter sedimentation, decantation and filtration other methods of separation separation methods

  1. chloride and sulphates of Mg and Ca

  2. bicarbonate of Na and K

  3. carbonate of Na and K

  4. none of these

Show answer
Correct Option: A