Tag: chemistry

Questions Related to chemistry

Process of conversion of wood into coal by biochemical process, taking over millions of years is called:

allotropes of carbon chemistry occurrence of carbon compounds in nature polymers

  1. catenation

  2. carbonation

  3. pyrolysis

  4. destructive distillation

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Correct Option: B
Explanation:

The Process of conversion of wood into coal by biochemical process is known as Carbonization. Coal burns cleaner than wood burning coal was easier because coal burned longer than wood.

Carbonization is the term for the conversion of an organic substance into carbon or a carbon-containing residue through pyrolysis or destructive distillation. It is often used in organic chemistry with reference to the generation of coal gas and coal tar from raw coal.

When super heated steam is passed through white hot wood charcoal, it gets reduced to a mixture of $X, Y$ and this reaction is named as $Z$. Identify $Y$.

allotropes of carbon chemistry occurrence of carbon compounds in nature polymers

  1. $C{O} _{2}$

  2. $S{O} _{2}$

  3. ${H} _{2}$

  4. $N{O} _{2}$

Show answer
Correct Option: C
Explanation:
$X + Y \longrightarrow CO + H _2(water-gas)$
$X = CO$
$Y = H _2$
$XY = water- gas (CO + H _2)$ reaction is exothermic.

$Z$ is known as $carbonisation$ reaction.
Hence, the correct option is C.

When super heated steam is passed through red hot wood charcoal, it gets reduced to a mixture of $X$ and $Y$ and this mixture is named as $Z$. Identify the mixture $Z$.

allotropes of carbon chemistry occurrence of carbon compounds in nature polymers

  1. Producer gas

  2. Water gas

  3. Coal gas

  4. Soda water

Show answer
Correct Option: B
Explanation:

When super heated steam is passed through hot wood charcoal then reaction takes place as


$C + H _2O \rightarrow CO + H _2$

The combination of $CO$ and $H _2$ is known as water gas.

${ C } _{ 12 }{ H } _{ 22 }{ O } _{ 11 }\xrightarrow { \quad \quad Conc.{ H } _{ 2 }S{ O } _{ 4 }\quad \quad  } 12C+11{ H } _{ 2 }O$
Which of the following is obtained by the above reaction?

allotropes of carbon chemistry occurrence of carbon compounds in nature polymers

  1. Animal charcoal

  2. Sugar charcoal

  3. Coke

  4. Wood charcoal

Show answer
Correct Option: B
Explanation:

Sugar when treated with con. $H _2SO _4$ it gives carbon as sugar charcoal and water.

${ C } _{ 12 }{ H } _{ 22 }{ O } _{ 11 }\xrightarrow { \quad \quad Conc.{ H } _{ 2 }S{ O } _{ 4 }\quad \quad  } 12C+11{ H } _{ 2 }O$

In the preparation of wood charcoal, liquid pyroligneous acid is obtained. It consists of:

allotropes of carbon chemistry occurrence of carbon compounds in nature polymers

  1. acetone

  2. methanol

  3. acetic acid

  4. Vinegar

Show answer
Correct Option: A,B,C
Explanation:

In the preparation of wood charcoal, liquid pyroligneous acid is obtained. It consists of acetone, methanol and acetic acid.

The anionic sites occupied by unpaired electrons are called F-centers or colour centers. They impart ______ $(X)$ colour to the crystals on $NaCl.$ Excess of lithium makes $LiCl$ crystals ______ $(Y)$ and excess of potassium makes $KCl$ crystals ______ $(Z)$. $(X)$, $(Y)$ and $(Z)$ are:

chemistry solid state imperfections in solids

  1. yellow, green and pink respectively.

  2. pink, yellow and violet (or lilac) respectively.

  3. yellow, pink and violet (or lilac) respectively.

  4. red, yellow and pink respectively,

Show answer
Correct Option: C
Explanation:

$NaCl$ shows the metal excess defect, which results in the formation of an F-center in the crystal. When light falls on this crystal, the electron in F-center gets excited. This F-center is then responsible for the yellow $(X)$ color of $NaCl$.

In a similar way, the excess of lithium imparts Pink $(Y)$ colour of $LiCl$ crystals.
In a similar way, the excess of potassium imparts violet/lilac $(Z)$ colour of $KCl$ crystals.

$F-$centres are :

chemistry solid state imperfections in solids

  1. the electrons trapped in anionic vacancies

  2. the electron trapped in cationic vacancies

  3. non-equivalent sites of stoichiometric compound

  4. All of the above

Show answer
Correct Option: A
Explanation:

$F$-centres or colour centres are points in a crystalline compound at which negative ion missing is replaced by one or more unpaired electrons. 


Hence, they are electrons trapped in anionic vacancies.

Therefore, the option is A.

The incorrect statement is :

chemistry solid state imperfections in solids

  1. When crystals of NaCI are heated in an atmosphere of sodium vapour, it appears yellow due to F-centres.

  2. $ O _2 $ is paramagnetic , $ CrO _2 $ is Ferromagnetic and $ MnO $ is anti-Ferromagnetic

  3. Certain oxides $ VO, VO _2VO _3 $ and $ TiO _3 $ show metallic properties at all temperatures.

  4. CCP & HCP have same coordination number.

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Correct Option: C

The correct statement regarding $F-$centre is:

chemistry solid state imperfections in solids

  1. electron are held in the voids of crystals

  2. $F-$centre produces colour to the crystals

  3. conductivity of the crystal increases due to $F-$centre

  4. all of the above

Show answer
Correct Option: D
Explanation:

$F-$ centre is a type of crystallographic defect in which an anionic vacancy in a crystal is filled by one or more unpaired electron, depending on the charge of the missing ion in the crystal. These unpaired electrons produces colour in the crystal by absorbing light in the visible spectrum. The unpaired electron acts as charge carriers and hence the crystal conducts electricity.

The presence of excess sodium in sodium chloride makes the crystal appearance yellow. This is due to the presence of

chemistry solid state imperfections in solids

  1. Schottky defect

  2. Frenkel defect

  3. F-centres

  4. Interstitial defects

Show answer
Correct Option: C