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 p- block elements-ii compounds of phosphorus- pcl5 phosphorus halides compounds of phosphorus compounds of phosphorus - pcl3

In the following reactions :
$(i) P{Cl} _{5}+{SO} _{2}\rightarrow A+B$
$(ii) A+MeCOOH\rightarrow C+{SO} _{2}+HCl$
$(iii) 2C+{Me} _{2}Cd\rightarrow 2D+CD{Cl} _{2}$ The compound (C) is:

  1. $Me-CH -Cl _2$
  2. $Me-CH _2 -Cl$
  3. $Me-\underset { \parallel \\ O }{ C } -Cl$
  4. $Me-C -Cl _3$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$(i) P{Cl} _{5}+{SO} _{2}\rightarrow SO{Cl} _{2} (A)+PO{cl} _{3} (B)$

(ii) $SO{Cl} _{2}+MeCOOH\rightarrow Me-\underset { \parallel \ O }{ C } -Cl (C)+{SO} _{2}+HCl\$

Multiple choice chemistry further aspects of equilibria indicators and acid-base titration study of indicators properties of acids and bases

Dissociation of ${ CH } _{ 3 }COOH$ is suppressed by adding

  1. HCL
  2. ${ H } _{ 2 }{ SO } _{ 4 }$
  3. $CH _{ 3 }COONa\quad$

  4. Any of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

CH3COOH is a weak acid. Adding CH3COONa provides a common ion (CH3COO-), which shifts the equilibrium of the weak acid dissociation to the left, suppressing it according to Le Chatelier's principle.

Multiple choice chemistry phenomena around us changes and its classification types of changes classification of changes

Which of the following is true?

  1. Melting of ice is reversible change.

  2. Burning of magnesium is reversible change.

  3. Rusting of iron is reversible change.

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

The statement (A) is true.
Melting of ice is reversible change.
Burning of magnesium is irreversible change.
Rusting of iron is irreversible change.

Multiple choice chemistry phenomena around us changes and its classification types of changes classification of changes

Burning of Magnesium ribbon is a _______

  1. Chemical change

  2. Physical change

  3. Reversible change

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

Magnesium ribbon burns with dazzling light in air and forms magnesium oxide.
$2Mg+O _2\rightarrow 2MgO$.
The above change is a chemical changes as new substance is  formed after change. Original
substances cannot be retrieved by simple physical processes.So it is chemical change.
Hence option A is correct.

Multiple choice chemistry phenomena around us changes and its classification types of changes classification of changes

Calcium carbide produces acetylene on reaction with water. Ethylene can be obtained by reduction of ${C} _{2}{H} _{2}$. Polythene is produced by polymerization of ${C} _{2}{H} _{4}$. Calculate the theoretical yield of polythene per kilogram of $Ca{C} _{2}$ :

  1. $0.6457kg$
  2. $0.4375kg$
  3. $0.5113kg$
  4. $0.3948kg$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Calcium carbide (CaC2) reacts with water to form acetylene (C2H2). Acetylene is reduced to ethylene (C2H4), which is then polymerized to form polythene (CH2CH2)n. Stoichiometric calculation shows 1 mole of CaC2 produces 1 mole of C2H2, which produces 1 mole of C2H4, resulting in 28g of ethylene units per 64g of CaC2.

Multiple choice chemistry chemical reactions of organic compounds commercially important alcohols - methanol methanol some commercially important alcohols uses of alcohols

$(CO+H _{2})+H _{2}\overset {673k,300atm,/Cr _{2}O _{3}-ZnO} {\rightarrow}$ 
The above shown reaction may by used for manufacture of:

  1. $HCHO$
  2. $CH _{3}COOH$
  3. $HCOOH$
  4. $CH _{3}OH$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Methanol is prepared on an industrial scale from a mixture of CO and H2. The mixture is subjected to 200atm pressure and passed over ZnO and Cr2O3 catalyst at 400 to 450 degrees celsius.

Multiple choice chemistry study of compounds a. hydrogen chloride laboratory method of preparation of hydrochloric acid physical and chemical properties and uses of hydrochloric acid hydrogen chloride: occurrence, preparation, purification and identification

The reaction equation of the preparation of $HCl$ by synthesis is given by:

  1. $NaCl + H _2SO _4 \rightarrow NaHSO _4+HCl$
  2. $NaHSO _4+NaCl \rightarrow HCl+NaSO _4$
  3. $H _2+Cl _2 \rightarrow 2HCl$

  4. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
In the chloralkali process, brine (mixture of sodium chloride and water) solution is electrolyzed producing chlorine (Cl$ _2$), sodium hydroxide, and hydrogen (H$ _2$):

2 NaCl + 2 H$ _2$O → Cl$ _2$ + 2 NaOH + H$ _2$

The pure chlorine gas can be combined with hydrogen to produce hydrogen chloride in the presence of UV light:

Cl$ _2$(g) + H$ _2$(g) → 2 HCl(g)

As the reaction is exothermic, the installation is called an HCl oven or HCl burner. The resulting hydrogen chloride gas is absorbed in deionized water, resulting in chemically pure hydrochloric acid. This reaction can give a very pure product, e.g. for use in the food industry.

Hence, the correct option is $\text{C}$
Multiple choice chemistry study of compounds a. hydrogen chloride laboratory method of preparation of hydrochloric acid physical and chemical properties and uses of hydrochloric acid hydrogen chloride: occurrence, preparation, purification and identification

HCl can be prepared by:

  1. $NaCl$ + $H _{2}SO _{4}$$\overset{420K}\rightarrow$
  2. $NaHSO _{4}$ + $NaCl$ $\overset{823K}\rightarrow$
  3. $NaNO _3$ + $H _{2}SO _{4}$ $\rightarrow$

  4. both (A) and (B).
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
HCl can be prepared by following :

$NaCl$ + $H _{2}SO _{4}$$\overset{420K}\rightarrow NaHSO _4+HCl$

$NaHSO _{4}$ + $NaCl$ $\overset{823K}\rightarrow Na _2SO _4+HCl$.

Hence option D is correct.
Multiple choice chemistry study of compounds a. hydrogen chloride laboratory method of preparation of hydrochloric acid physical and chemical properties and uses of hydrochloric acid hydrogen chloride: occurrence, preparation, purification and identification
Formation of $HCl$ from its elements takes place in the presence of sunlight.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Hydrogen chloride is prepared from chlorine gas and hydrogen gas in the presence of UV light. This reaction is exothermic and the resulting HCl gas is absorbed in deionized water.

${ H } _{ 2 }+{ Cl } _{ 2 }\rightarrow 2HCl$

Multiple choice chemistry study of compounds a. hydrogen chloride laboratory method of preparation of hydrochloric acid physical and chemical properties and uses of hydrochloric acid hydrogen chloride: occurrence, preparation, purification and identification

When phosphorous pentoxide is reacted with $HCl$ gas, products are:

  1. $POCl _3$
  2. $P _4O _{10}$
  3. $H _3PO _2$
  4. $HPO _3$
Reveal answer Fill a bubble to check yourself
A,D Correct answer
Explanation

Phosphorous pentoxide reacts with $HCl$ to form Phosphorous Oxychloride and metaphosphoric acid.


$2P _2O _5 + 3HCl \rightarrow POCl _3 + 3HPO _3$


Hence, $POCl _3$ and $HPO _3$ are correct.

Multiple choice chemistry study of compounds a. hydrogen chloride laboratory method of preparation of hydrochloric acid physical and chemical properties and uses of hydrochloric acid hydrogen chloride: occurrence, preparation, purification and identification

In the Hydrolysis of ICl , the products are :

  1. HI +HCl

  2. HI +HOCl

  3. HCl+HOI

  4. HOCl +HOI
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In the hydrolysis of ICl, the products are HCl + HOI.


$ICl+H _2O\rightarrow HCl+HOI$

During the hydrolysis of interhalogen compounds, oxyacid of less electronegative or large sized halogen is formed, and other halogen forms halogen acid. 

Thus, less electronegative iodine forms HOI and more electronegative chlorine forms HCl.

Multiple choice chemistry lattice energy born-haber cycle born-haber cycles energy cycles

The standard formation reaction for aluminium oxide is $4Al(s) + 6O(g)\rightarrow 2Al _2O _3(s)$. This statement is false because:

  1. aluminium is not in its standard state

  2. the reaction should be written for one mole of Al
  3. The reaction is prevented by a thin film of $Al _2O _3$ formed on the surface of Al

  4. none of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
$2Al+3O _2\rightarrow Al _2O _3$

The enthalpy of the above reaction is enthalpy of formation as one mole of $Al _2O _3$ is forming from elemental aluminum and oxygen gas. 
Multiple choice aluminium patterns and properties of metals chemistry

${ aAl } _{ 2 }{ \left( { C } _{ 2 }{ O } _{ 4 } \right)  } _{ 3 }(s)\xrightarrow [  ]{ \Delta  } \quad { bAl } _{ 2 }{ O } _{ 3 }(s)+cCO(g)+d{ CO } _{ 2 }(g)$
According to the equation for the reaction represented above, what is the mole of $CO$ to ${CO} _{2}$ that is produced by the decomposition of aluminium oxalate?

  1. $1$ mole $CO$; $1$ mole of ${CO} _{2}$
  2. $1$ mole $CO$; $2$ moles of ${CO} _{2}$
  3. $1$ mole $CO$; $3$ moles of ${CO} _{2}$
  4. $2$ moles $CO$; $1$ mole of ${CO} _{2}$
  5. $3$ moles $CO$; $1$ mole of ${CO} _{2}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

${ Al } _{ 2 }{ ({ C } _{ 2 }{ O } _{ 4 }) } _{ 3 }(s)\xrightarrow { \Delta  } { Al } _{ 2 }{ O } _{ 3 }(s)+3CO(g)+3C{ O } _{ 2 }(g)$

According to the equation for the reaction represented above, what is the mole of $CO$ to $C{ O } _{ 2 }$ that is produced by the decomposition of aluminium oxalate is 1 mole of $C{ O }$ : 1 mole of $C{ O } _{ 2 }$