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 botany photosynthesis modern concept of photosynthesis photosystems photosynthesis in higher plants

Hill reaction completes in the

  1. Light.

  2. Dark.

  3. Both A and B.

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

Hill reaction occurs in light or can be called as light reaction. Hill first of all demonstrated that isolated chloroplasts can release oxygen in presence of suitable inorganic electron acceptors. The Hill reaction is the light-driven transfer of electrons from water to Hill reagents (non-physiological oxidants) against a chemical potential gradient. 

Multiple choice chemistry petrochemicals and polymers petroleum properties of alkanes petroleum and natural gas rocks and minerals

The final product in the following reaction can be used as, $4CH _3-CH _2-Cl+4Na+Pb \rightarrow$

  1. anaesthatic

  2. narcotics

  3. analgesic

  4. antiknocking agent
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

  • The final product of this reaction is $(CH _3CH _2) _4Pb$ [tetraethyl lead (TEL)].
$4CH _3-CH _2-Cl + 4Na + Pb \rightarrow (CH _3CH _2) _4Pb$
It is also used as an antiknocking agent in fuels for automobiles.

Multiple choice chemistry p- block elements-ii group 16 elements - general properties group 16 elements - trends in chemical properties group 16 elements

In which one of the following reactions, a 16 group element will get precipitated ?

  1. $ Na _2S _2O _3 + CI _2+H _2O \longrightarrow $
  2. $ Na _2SO _3 - CI _2+H _2O \longrightarrow $
  3. $ SO _2+2H _2O+CI _2 \longrightarrow $
  4. $ 2FeSO _4+H _2SO _4+CI _2 \longrightarrow $
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In the reaction of sodium thiosulfate with chlorine, sulfur is precipitated as a solid product.

Multiple choice evs let's play with water law of constant proportion - i law of constant proportion law of definite proportions

Nitrogen reaction with oxygen to form nitrogen (III) oxide.


What will be the volume ratio of the reactants and products of the given reaction?

  1. 2 : 3 : 2

  2. 2 : 3 : 4

  3. 1 : 3 : 2

  4. 2 : 1 : 2
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$2 N _2 + 3 O _2 \rightarrow 2N _2 O _3$

reactants = $N _2 \, \& \, O _2$
Product = $N _2O _3$
Ratio are $2 : 3 : 2$ by law of constant proportions 
{stionchiometry coefficient) 


Multiple choice photosystems photosynthesis in plants metabolism, cell respiration, and photosynthesis photosynthesis in higher plants biology

$P _{680}$ is related with  

  1. PS- I

  2. PS- II

  3. Hill reaction

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

P$ _{680}$ is the primary donor present in photosystem II. Structurally,  it's chlorophyll pigment dimer is present at the center of photosystem II. 680 suggests that the absorption is maximum at 680nm in red light. P$ _{680}$ or primary donor receives energy either by absorbing light or by excitation of electrons present in nearby chlorophyll. The excited electrons get captured by electron acceptor present in photosystem II, which is pheophytin and oxidized P$ _{680}$ is then reduced by electron generated from water during oxygenic photosynthesis.

Multiple choice photosystems photosynthesis in plants metabolism, cell respiration, and photosynthesis photosynthesis in higher plants biology

Reaction centre of PS I is

  1. $P _{700}$
  2. $P _{680}$
  3. $Chl _{715}$
  4. $Chl _{685}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Each photosystem is characterized by the wavelength of light at which it's reaction center absorbs maximum light i.e., 700 and 680 nanometers, respectively for PS I and PS II in chloroplasts. thus PS I is denoted by P$ _{700}$. Thus, the correct answer is 'P$ _{700}$'.

Multiple choice chemistry general principles of metallurgy extraction of copper and zinc extraction of copper and zinc from their oxides basics of metallurgy

Following reactions take place during extraction of gold.
$4Au+8CN^-+2H _2O+O _2\rightarrow 4[Au(CN) _2]^-+4OH^-$
$2[Au(CN) _2]^-+Zn\rightarrow 2Au+[Zn(CN) _4]^{2-}$
Zinc in the extraction of gold acts as a/an:

  1. oxidising agent

  2. flux

  3. reducing agent

  4. decomposing agent
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
$4Au+8CN^-+2H _2O+O _2\longrightarrow 4[Au(CN) _2]^-+4OH^-$
$2[Au(CN) _2]^-+Zn\longrightarrow 2Au+[Zn(CN) _4]^{2-}$
                                 $0$                        $+2$
In the above reaction, Zinc is changing its states from $0$ to $+2$ so zinc is getting oxidized and it acts as reducing agent.
Multiple choice chemistry general principles of metallurgy extraction of copper and zinc extraction of copper and zinc from their oxides basics of metallurgy

$2Cu _{2}S + 3O _{2}(g)\xrightarrow {heat} {a} + {b}$

In the reaction above $a$ and $b$ are:

  1. $a = 2Cu _{2}O, b = 2SO _{2}$
  2. $a = 4CuO _{2}, b = 2SO _{3}$
  3. $a = 2CuO, b = 4SO _{2}$
  4. $a = 3CuS, b = 2SO _{2}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$2Cu _{2}S + 3O _{2} (g)\xrightarrow {\triangle} 2Cu _{2}O + 2SO _{2}(g)$
$2Cu _{2}O + Cu _{2}S\xrightarrow {\triangle} 6Cu(S) + SO _{2}(g)$.

Multiple choice chemistry general principles of metallurgy extraction of copper and zinc extraction of copper and zinc from their oxides basics of metallurgy

$Zn + NH _3 \quad\xrightarrow{\small{heat}} \quad ?$

  1. $ZnH _2 + N _2$
  2. $Zn _3N _2 + H _2$
  3. $Zn(NH _2) _2 + H _2$
  4. $[Zn(NH _3) _4]^{2+}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Zinc(II) ion forms complex ions readily.
Reaction of the process:
$Zn + xNH _3 \quad\xrightarrow{\small{red heat}} \quad Zn(NH _3) _x$
Where $x = 4$ to $6 $ 

Multiple choice enzymes and catalysts catalysis adsorption and colloids surface chemistry chemistry adsorption theory of heterogeneous catalysis

The process which is catalysed by one of the product is called :

  1. acid - base catalysis

  2. autocatalysis

  3. negative catalysis

  4. homogeneous catalysis
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A catalyst is a substance, which increases the rate of reaction without itself being consumed at the end of the reaction, and the phenomenon is called catalysis. There are some catalysts which decrease the rate of reaction and such catalysts are called negative catalyst. Obviously, the catalyst accelerating the rate will be positive catalyst. However, the term positive is seldom used and catalyst itself implies positive catalyst. Catalysts are generally foreign substances but sometimes one of the product formed may act as a catalyst and such a catalyst is called "auto catalyst" and the phenomenon is called auto catalysis.0
A chemical reaction is said to have undergone autocatalysis, if the reaction product itself is the catalyst for that reaction.

Multiple choice enzymes and catalysts catalysis adsorption and colloids surface chemistry chemistry adsorption theory of heterogeneous catalysis

Which of the following is used as autocatalyst

  1. $ KMnO _4 $
  2. $ AI _2O _3 $
  3. $ CaC _3 $

  4. All of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

KMnO4 is a classic example of an autocatalyst in the reaction between oxalic acid and acidified potassium permanganate, where Mn2+ ions produced during the reaction catalyze the process.