Chemistry

Chemical Reactions and Equations

674 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 hydrogen and its compounds heavy water study of heavy water hard water and soft water

$ \displaystyle 4{ D } _{ 2 }O+3Fe \xrightarrow[]{red-hot} Fe _{3}O _{4}+gas.$ The gas produced in the above reaction is:

  1. $ \displaystyle O _{2}$
  2. $ \displaystyle H _{2}$
  3. $ \displaystyle D _{2}$

  4. none
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Reaction:

$ \displaystyle 4{ D } _{ 2 }O+3Fe \xrightarrow[]{red-hot} Fe _{3}O _{4}+ D _2$. The gas produced in the reaction is deuterium.

Multiple choice separation of components of mixtures methods of separation elements, compounds and mixtures chemistry

If a steam-jacket eudiometer with $23ml$ of oxygen and $4ml$ of hydrogen are mixed over mercury, determine how much and which gas would be left as uncombined after the mixture is sparked?

  1. $21$mL $O _2$
  2. $3.0$mL $H _2$
  3. $24$mL $O _2$
  4. $28$mL $O _2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$\displaystyle  2H _2 + O _2 \rightarrow 2H _2O$
2 moles of hydrogen will react with 1 mole of oxygen.
Volume is directly proportional to the number of moles.
4 ml of hydrogen will react with $\displaystyle  \dfrac {4 \times 1}{2}= 2$  ml of oxygen.
$\displaystyle  23-2 = 21 ml$  of oxygen will be left uncombined.

Multiple choice separation of components of mixtures methods of separation elements, compounds and mixtures chemistry

If a steam-jacket eudiometer with 23ml of oxygen and 4ml of hydrogen are mixed over mercury, determine the total volume in ml of the gas after the mixture was sparked?

  1. $16$
  2. $25$
  3. $34$
  4. $36$
  5. $40$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$\displaystyle  2H _2 + O _2 \rightarrow 2H _2O$
2 moles of hydrogen will react with 1 mole of oxygen to form 2 moles of water.
Volume is directly proportional to the number of moles.
4 ml of hydrogen will react with $\displaystyle  \dfrac {4 \times 1}{2}= 2$  ml of oxygen to form 4 ml of water.
$\displaystyle  23-2 = 21 ml$  of oxygen will be left uncombined.
Thus, after the mixture was sparked, 21 ml oxygen and 4 ml water are present.
Total volume of the gas after the mixture was sparked $\displaystyle  = 21 + 4 = 25 $ ml.

Multiple choice chemistry reactivity series and electrochemistry reactivity series and displacement reactions chemical properties of metals chemical properties of metals and non metals

Which one of the following reactions does not occur?

  1. ${ F } _{ 2 }+2{ Cl }^{ - }\rightarrow 2{ F }^{ - }+{ Cl } _{ 2 }$
  2. ${ Cl } _{ 2 }+2{ F }^{ - }\rightarrow 2{ Cl }^{ - }+{ F } _{ 2 }$
  3. ${ Br } _{ 2 }+2{ I }^{ - }\rightarrow 2{ Br }^{ - }+{ I } _{ 2 }$
  4. ${ Cl } _{ 2 }+2{ Br }^{ - }\rightarrow 2Cl^-+{ Br } _{ 2 }$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

With progressive increase in atomic number, the reduction potential of halogens decreases, thus oxidising power also decreases. Hence, a halogen with lower atomic number will oxidise the halide ion of higher atomic number and therefore, will liberate them from their salt solution.
Hence, the reaction
${ Cl } _{ 2 }+2{ F }^{ - }\rightarrow 2{ Cl }^{ - }+{ F } _{ 2 }$
is not possible.

Multiple choice chemistry reactivity series and electrochemistry reactivity series and displacement reactions chemical properties of metals chemical properties of metals and non metals

X, Y, Z are three elements which undergo chemical changes according to the following equations:
$I:\, X _2O _3 + 2Y \rightarrow Y _2O _3 + 2X$
$II:\, Y _2O _3 + 3Z \rightarrow 3ZO + 2Y$
The order of increasing reactivity is:

  1. X < Y < Z

  2. Y < X < Z

  3. Z < X < Y

  4. Z < Y < X
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Y has displaced X in reaction I. So, Y is more reactive than X.
Z has displaced Y is reaction II. So, Z is more reactive than Y. 

Thus, Z is most reactive and X is the least reactive.

Multiple choice chemistry reactivity series and electrochemistry reactivity series and displacement reactions chemical properties of metals chemical properties of metals and non metals

In the reaction between $Al$ and $Fe _2O _3$, what is the correct final reaction?

  1. $Al+Fe _2O _3 \rightarrow Al _3O _2+2Fe$
  2. $2Al+Fe _2O _3 \rightarrow Al _2O _3+2Fe$
  3. $Al+Fe _2O _3 \rightarrow Al _2O _3+Fe _2$
  4. $Al+Fe _2O _3 \rightarrow Al _2O _3+2Fe$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Al will displace iron from solution.
$\displaystyle  2Al+Fe _2O _3 \rightarrow Al _2O _3+2Fe$

Multiple choice chemistry reactivity series and electrochemistry reactivity series and displacement reactions chemical properties of metals chemical properties of metals and non metals

$Li$, $K$, $Ca$, $Na$, $Mg$, $Al$, $Zn$, $Fe$, $Pb$, $Cu$, $Hg$, $Ag$
$I$. The reaction $3Fe(s)+2Al{({NO} _{3})} _{3}(aq)\rightarrow 2Al(s)+3Fe{({NO} _{3})} _{2}(aq)$ will occur.
$II$. Iron is higher on the activity series than aluminum.

  1. Statement $I$ is true, Statement $II$ is true and is a correct explanation of the phenomena described in $I$
  2. Statement $I$ is true, Statement $II$ is false
  3. Statement $I$ is false, Statement $II$ is true
  4. Statement $I$ is false, Statement $II$ is false
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

By using the reactivity series of metals, one can predict the products of displacement reactions . Each element in the reactivity series can be replaced from a compound by any of the elements above it. For ex: $Mg$ can replace $Zn$ from the solution. 

$Al$ is higher on the activity series than $Fe$.
Therefore $Fe$ can not displace $Al$ from $Al{(NO _3)} _3$
$\therefore 3Fe+2Al{(NO _3)} _3\longrightarrow 2Al+3Fe{(NO _3)} _2$ will not occur.