Tag: chemistry

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

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

  1. providing an inert atmosphere

  2. cooling the blast chamber

  3. reducing friction

  4. displacing hot air
Reveal answer Fill a bubble to check yourself
A Correct answer
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.
Multiple choice chemistry nitrogen and sulfur nitrogen gas component of air - nitrogen nitrogen

Which of the following is not a nitrogenous fertilizer ?

  1. Calcium cyanamide

  2. CAN

  3. Super phosphate of lime

  4. Urea
Reveal answer Fill a bubble to check yourself
C Correct answer
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.
Multiple choice chemistry nitrogen and sulfur nitrogen gas component of air - nitrogen nitrogen

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

  1. $N _2$
  2. $NH _2$
  3. $NO _2$

  4. none of these
Reveal answer Fill a bubble to check yourself
B Correct answer
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 $NH _2$.

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

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:

  1. $90\ gm\ { min }^{ -1 }$
  2. $46\ gm\ { min }^{ -1 }$
  3. $28\ gm\ { min }^{ -1 }$
  4. $32\ gm\ { min }^{ -1 }$
Reveal answer Fill a bubble to check yourself
A Correct answer
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.
Multiple choice chemistry separation of matter sedimentation, decantation and filtration other methods of separation separation methods

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

  1. sublimation

  2. centrifugation

  3. winnowing

  4. evaporation
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

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

  1. Mechanical separation

  2. Magnetic separation

  3. Gravity separation

  4. All of above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Solid-solid mixtures can be separated using various physical methods depending on the properties of the components, such as mechanical picking, magnetic properties, or density differences (gravity).

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

Water is said to be permanently hard when it contains:

  1. chloride and sulphates of Mg and Ca

  2. bicarbonate of Na and K

  3. carbonate of Na and K

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Permanent hardness in water is caused by the presence of dissolved chlorides and sulfates of calcium and magnesium, which cannot be removed by boiling.