Chemistry

Chemical Reactions and Equations

684 Questions

Chemical reactions and equations form a foundational chemistry topic where students identify reaction products, balance chemical formulas, and classify reaction types. It covers critical mechanisms like Markovnikov's rule, precipitation, and endothermic or exothermic processes. These questions are highly common in general science sections of state and central government competitive exams.

Endothermic reactionsPrecipitation reactionsDehydrohalogenation of alkyl halidesChemical equation balancingReaction product identification

Chemical Reactions and Equations Questions

Multiple choice chemistry chemical reactions and equations kinetic study of some first order reactions rate of chemical reaction endothermic and exothermic reactions

For the reaction $2N _2O _5\, \rightarrow\, 4NO _2\, +\, O _2$, if $\displaystyle -\, \frac{d[N _2O _5]}{dt}\, =\, k _1[N _2O _5]$, $\displaystyle \frac{d[NO _2]}{dt}\, =\, k _2[N _2O _5]$, $\displaystyle \frac{d[O _2]}{dt}\, =\, k _3[N _2O _5]$.
What is the relation between $k _1, k _2$ and $k _3$?

  1. $k _1\, =\, k _2\, =\, k _3$
  2. $2k _1\, =\, k _2\, =\, 4k _3$
  3. $2k _1\ =\, 4k _2\, =\, k _3$

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

As we know, for a reaction: $2N _2O _5\, \rightarrow\, 4NO _2\, +\, O _2$

$\displaystyle -\, \frac{1}{2}\, \frac{d[N _2O _5]}{dt}\, =\, \frac{1}{4}\, \frac{d[NO _2]}{dt}\, =\, \frac{d[O _2]}{dt}$

So, $2k _1\, =\, k _2\, =\, 4k _3.$

Multiple choice chemistry chemical kinetics kinetic study of some first order reactions rate of chemical reaction endothermic and exothermic reactions

Benzene diazonium chloride (A) decomposes into chloro-benzene (B) and ${{\text{N}} _{\text{2}}}\left( {\text{g}} \right)$ in first order reaction volume of ${{\text{N}} _2}$ collected after 5 min and at the complete decomposition of A are 10 ml and 50 ml respectively. The rate constant for the reaction is:

  1. 0.446 ${\min ^{ - 1}}$
  2. 0.0446 ${\min ^{ - 1}}$
  3. 0.223 ${\min ^{ - 1}}$
  4. 0.112 ${\min ^{ - 1}}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

t = 0

                              $\mathop {\text{A}}\limits _{50}  \to \mathop {\text{B}}\limits _0  + \mathop {{{\text{N}} _2}}\limits _0 $
At t = 5 min.    50 - 10          10 ml
t = complete                          50 ml
          $\ln  = \left( {\dfrac{{50}}{{40}}} \right) = {\kappa _1} \times 5$
  $\dfrac{{0.223}}{5} = {\kappa _1} \Rightarrow 0.0446\,{\min ^{ - 1}}$
Hence, option (B) is correct.

Multiple choice chemistry chemical kinetics kinetic study of some first order reactions rate of chemical reaction endothermic and exothermic reactions

For the decomposition of $H _2O _2(aq.)$, it was found that $V _{O _2} (t=15 min.)$ was 100 mL (at 0$^oC$ and 1 atm) while $V _{O _2}$ (maximum) was 200 mL (at 0$^oC$ and 2 atm). If the same reaction had been followed by the titration method and if $V _{KMnO _4}^{cM} (t = 0)$ had been 40 mL, what would $V _{KMnO _4}^{cM}(t = 15 min)$ have been?

  1. 30 mL

  2. 25 mL

  3. 20 mL

  4. 15 mL
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

200 ml at 2 atm corresponds to 400 ml at 1 atm. This is the maximum value
In 15 minutes, the volume is 100 ml.
Thus one fourth of the reaction is complete in 15 minutes.
Hence, the volume of $KMnO _4$ will be $\displaystyle \frac{3}{4} \times 40 = 30 mL$

Multiple choice chemistry chemical kinetics kinetic study of some first order reactions rate of chemical reaction endothermic and exothermic reactions

Which of the following are example of pseudo unimolecular reactions?
1. Inversion of cane sugar
2. Decomposition of ozone
3. Decomposition of $N _{2} O _{5}$
4. Acid catalysed by hydrolysis of ester

  1. 2 and 4

  2. 1 and 4

  3. 1, 2 and 4

  4. 1, 2, 3 and 4
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Inversion of cane sugar and Acid catalyzed by hydrolysis of ester are examples of pseudo unimolecular reactions.
Decomposition of ozone is a bimolecular reaction.
Decomposition of dintirogen pentoxide is also a bimolecular reaction.

Multiple choice chemistry basic concepts of chemistry law of multiple proportion law of multiple proportions laws of chemical combination

Among the following pairs of compounds, the one that illustrates the law of multiple proportions is:

  1. $NH _{3}$ and $NCl _{3}$
  2. $H _{2}S$ and $SO _{2}$
  3. $CuO$ and $Cu _{2}O$
  4. $CS _{2}$ and $FeSO _{4}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

According to the concept of law of multiple proportions, if two elements chemically combine to give two or more compounds, then the weight of one element which combines with the fixed weight of the other element in those compound, bear simple multiple ratios to one another.


Hence, $CuO$ and $CU _2O$ form two different compounds in a ratio of 1:2 with the fixed weight of oxygen.

Multiple choice chemistry basic concepts of chemistry law of multiple proportion law of multiple proportions laws of chemical combination

Among the following pairs,the one which illustrates the law of multiple proportions is_____.

  1. $NH _3, \ HCl$
  2. ${ H } _{ 2 }S,{ SO } _{ 2 }$
  3. $CuO,{ Cu } _{ 2 }O$
  4. ${ CS } _{ 2 },{ FeSO } _{ 4 }$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The law of multiple proportions applies to pairs of compounds formed by the same two elements. CuO and Cu2O are both formed by copper and oxygen, making them the correct pair.

Multiple choice chemistry basic concepts of chemistry law of multiple proportion law of multiple proportions laws of chemical combination

Law of multiple proportions is illustrated by which of the following pairs of compounds?

  1. $HCl$ and $HNO _{3}$
  2. $KOH$ and $KCl$
  3. $N _{2}O$ and $NO$
  4. $H _{2}S$ and $SO _{2}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A fixed mass of nitrogen, say $100$ grams, may react with $57.14$ grams of oxygen to produce one oxide, or with $114.28$ grams of oxygen to produce the other. The ratio of the masses of oxygen that can react with $100$ grams of nitrogen is $57.14:114.28$ or  $2:1$, a ratio of small whole numbers.

Multiple choice chemistry basic concepts of chemistry law of multiple proportion law of multiple proportions laws of chemical combination

For describing law of multiple proportions, which among the following pair can be used?

  1. NO and $NO _2$
  2. $CH _4$ and $CO _2$
  3. $ZnO _2$ and $ZnCl _2$
  4. $NH _3$ and $NH _4Cl$
  5. $H _2O$ and HCl
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

For describing law of multiple proportions, the pair $\displaystyle  NO$ and $\displaystyle  NO _2$ can be used.
According to the law of multiple proportions, if two elements combine to form more than one compound, then the different masses of one element which combine with fixed mass of other element, bear a simple ratio to one another.
In the pair $\displaystyle  NO$ and $\displaystyle  NO _2$, we have two elements N and O that combine to form more than one compound. In all other examples, more than two elements are present.

Multiple choice chemistry basic concepts of chemistry law of multiple proportion law of multiple proportions laws of chemical combination

Which of the following pairs illustrates the law of multiple proportions?

  1. $PH _3$, $HCl$
  2. $PbO$, $PbO _2$
  3. $H _2S$, $SO _2$
  4. $CuCl _2$, $CuSO _4$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

the law of multiple proportions.: two elements combine to form more than one compound and the masses of one element that combine with a fixed mass of the other element is in the ratio of small whole numbers. 

So all elements are same only the mass ratio of reactants varies the product formation.
thus in $PbO$ and $PbO _2$ the reactants are $Pb$ and $O _2$ that combine in different ratio. other options do not have all the elements common.
option B is correct

Multiple choice chemistry basic concepts of chemistry law of multiple proportion law of multiple proportions laws of chemical combination

Law of multiple proportions is illustrated by which one of the  following pairs ?

  1. $H _{2}S$ and $SO _{2}$
  2. $NH _{3}$ and $NO _{2}$
  3. $N _{2}O$ and NO
  4. $N _{2}S$ and $Na _{2}O$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Law of multiple proportions say that if 2 elements form more than one compounds between them, then the ratios of the masses of the second element which combine with a fixed mass of the first element will be ratios of small whole numbers.
In $N _{2}O$ and $NO$, the ratio of weight of $N$ reacting with a constant weight of $O$ is $2:1$

Multiple choice chemistry hard water and soft water heavy water study of heavy water hydrogen and its compounds

Which of the following is not a deuterolysis reaction

  1. $SO _{3}+D _{2}O\rightarrow D _2SO _{4}$
  2. $CaC _{2}+2D _{2}O\rightarrow Ca(OD) _{2}+C _{2}D _{2}$
  3. $Mg _{3}N _{2}+6D _{2}O\rightarrow 3Mg(OD) _{2}+2ND _{3}$
  4. $AlCl _{3}3D _{2}O\rightarrow Al(OD) _{3}+3DCl$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Option $A$ is not a deuterolysis reaction. It is not a chemical reaction at all. 

Deuterolysis reactions are reactions in which a salt reacts with heavy water to give a base and an acid.