Tag: chemistry

Quizzes (490) Questions (9892)

Questions Related to chemistry

Multiple choice chemistry the p-block elements - group 13 study of diborane some important compounds of boron study of boron

A compound $A$ of boron reacts with $NMe _3$ to give an adduct $B$ which on hydrolysis gives a compound $C$ and a gas $D$. Compound $C$ is an acid.

Compound $C$ is :

  1. diborane

  2. boric acid

  3. borate salt

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

     $B _2H _6+2NMe _3\longrightarrow 2BH _3.NMe _3$

Diborane (A)                        Adduct (B)

$BH _3.NMe _3+3H _2O\longrightarrow H _3BO _3+NMe _3+3H _2$
                                                Boric acid                     $\downarrow$
                                                      (C)                          (D) gas

Compound "C" is boric acid $-H _3BO _3$

Multiple choice chemistry the p-block elements - group 13 study of diborane some important compounds of boron study of boron

A compound $A$ of boron reacts with $NMe _3$ to give an adduct $B$ which on hydrolysis gives a compound $C$ and a gas $D$. Compound $C$ is an acid.


Compound $A$ is :

  1. diborane

  2. boric acid

  3. borate salt

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

     $B _2H _6+2NMe _3\longrightarrow2BH _3.NMe _3$

Diborane (A)                        Adduct (B)

$BH _3.NMe _3+3H _2O\longrightarrow H _3BO _3+NMe _3+3H _2$
                                               Boric acid                      $\downarrow$
                                                    (C)                            (D) gas
Compound $A$ is diborane.

Multiple choice chemistry the p-block elements - group 13 study of diborane some important compounds of boron study of boron

An alkali metal hydride (NaH) react with diborane in 'A' to give a tetrahedral compound 'B' which is extensively used as reducing agent in organic synthesis. The compounds 'A' and 'B' respectively are :

  1. $CH _3COCH _3\,\,\, and \,\,\,B _3N _3H _6$
  2. $(C _2H _5) _2O \,\,\,and\,\,\, NaBH _4$
  3. $C _2H _6\,\,\,and\,\,C _2H _5Na$
  4. $C _6H _6\,\,\,and\,\,\,NaBH _4$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Answer:-
When an alkali metal hydride $(NaH)$ react with diborane $({B} _{2}{H} _{6})$ in the presence of ether $({({C} _{2}{H} _{5})} _{2}O)$, a tetrahedral compound (Metal borohydride) is formed which act as a reducing agent in organic synthesis.
$2NaH + {B} _{2}{H} _{6} \; \xrightarrow{{({C} _{2}{H} _{5})} _{2}O} \; \underset{\text{sodium borohydride}}{2NaB{H} _{4}}$
Thus, A is  ${({C} _{2}{H} _{5})} _{2}O$ and B is $NaB{H} _{4}$.
Multiple choice chemistry the p-block elements - group 13 study of diborane some important compounds of boron study of boron

A compound $X$, of boron reacts with $NH _3$ on heating to give another compound $Y$ which is called inorganic benzene. The compound $X$ can be prepared by treating $BF _3$ with lithium aluminum hydride. The compounds $X$ and $Y$ are represented by formula:

  1. $B _2H _6, B _3N _3H _6$
  2. $B _2O _3, B _3N _3H _6$
  3. $BF _3, B _3N _3H _6$
  4. $B _3N _3H _6, B _2H _6$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
A compound $X$, of boron, reacts with $N{H} _{3}$ on heating to give another compound $Y$ which is called inorganic benzene.
$\underset{X \; (Diborane)}{3{B} _{2}{H} _{6}} + 6N{H} _{3} \longrightarrow 3{[B{H} _{2}{(N{H} _{3})} _{2}]}^{+}{[B{H} _{4}]}^{-} \xrightarrow{heat} \underset{\text{Y (Borazole/Inorganic Benzene)}}{2{B} _{3}{N} _{3}{H} _{6}} + 12{H} _{2}$
$4B{F} _{3} + 3LiAl{H} _{4} \longrightarrow \underset{X}{2{B} _{2}{H} _{6}} +3LiF + 3Al{F} _{3}$
Multiple choice chemistry air and water pollution control environmental impact: global warming green house effect geobiochemical cycle

Increased level of greenhouse gases causes global warming which will result in:

  1. biomagnification

  2. eutrophication

  3. melting of glaciers

  4. ozone depletion
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The earth's atmosphere traps the heat from the sun, preventing it from escaping into space is the greenhouse effect. This is mainly caused by deforestation. This results in an increase in average temperature of the atmosphere due to which glaciers start melting and there is a rise in sea level. 

Multiple choice chemistry pollution of air and water environmental impact: global warming green house effect geobiochemical cycle

Which of the following is not a refrigerant?

  1. $CHClF _{2}$
  2. $NH _{3}$
  3. $Ether$
  4. $C _{2}H _{4}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Ethene is a colorless flammable gas with a faint "sweet and musky" odor when pure.
Ethylene is widely used in chemical industry. Ethylene is also an important natural plant hormone, used in agriculture to force the ripening of fruits. it is a non refrigerant.