Chemistry

Chemical Reactions and Processes

626 Questions

Chemical reactions and processes questions cover the transformation of substances through electrolysis, thermal decomposition, and catalysis. Key areas include identifying gas evolution, balancing chemical equations, and understanding industrial chemical applications. This general chemistry topic is a staple in the science sections of multiple competitive examinations.

Thermal decompositionElectrolysis processGas evolution reactionsHeterogeneous catalystsFuel cell components

Chemical Reactions and Processes Questions

Multiple choice chemistry p- block elements-ii hydrogen chloride chlorine - 17 group p-block elements

What if hydrochloric acid comes in contact with a metal such as magnesium?

  1. Liberate $H _2$ gas
  2. Liberate $Cl _2$ gas
  3. Precipitate $Mg$

  4. No reaction will take place
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Metals that are more reactive than hydrogen, such as magnesium, react with hydrochloric acid to produce a metal chloride salt and hydrogen gas.

Multiple choice chemistry p- block elements-ii hydrogen chloride chlorine - 17 group p-block elements

A glass rod dipped in ammonia solution is brought near the mouth of the $HCl$ gas, then:

  1. deep red flame of ammonium chloride appears

  2. dense white fumes of ammonium chloride appears

  3. no reaction occurs

  4. none of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
When a glass rod dipped in the ammonia solution is brought near HCl gas, a dense white fume of ammonium chloride is formed.
This is because ammonia reacts with the fumes of $HCl$ to give ammonium chloride.
$NH _3 + HCl \rightarrow NH _4Cl$
Multiple choice chemistry p- block elements-ii hydrogen chloride chlorine - 17 group p-block elements

$CaO(s)+H _3O^++Cl^-\longrightarrow$
Addition of solid calcium oxide to a solution of hydrochloric acid as given, results in the formation of:
(1) $Ca^{2+}$
(2) $H _2O$
(3) $H _2$

  1. If 1, 2 and 3 are correct

  2. If only 1 and 2 are correct

  3. If only 2 and 3 are correct

  4. If only 1 is correct

  5. If only 3 is correct
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$CaO+2HCl \rightarrow CaCl _2+H _2O$

In this reaction, due to water, quick lime is converted into slaked lime, which on reaction with hydrochloric acid gives calcium chloride and water.

Multiple choice chemistry p- block elements-ii hydrogen chloride chlorine - 17 group p-block elements
   Appearance   Reactions with dilute$HCl$ Reaction with Dilute$HNO _3$ 
 Unknown metal 1  Dull grey solid with white oxide coating  Dissolved with bubbles of clear gas  Dissolved with bubbles of clear gas
 Unknown metal 2  Solid, lustrous, smooth silver-grey surface  No reaction   Dissolved with bubbles of orange gas

Identify the gas(transparent) produced with the addition of dilute $HCl$ to unknown metal 1.

  1. ${Cl} _{2}$
  2. ${H} _{2}$
  3. ${O} _{2}$
  4. $C{O} _{2}$
  5. $N{O} _{2}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Metals reacts with $HCl$ to liberate hydrogen gas.

Multiple choice chemistry substances in common use preparation, properties and uses of baking soda chemical from common salt compounds of carbon

When we add a pinch of sodium hydrogen carbonate in a flask containing ethanoic acid a reaction takes place. What will be the observation when we carry out the reaction?

  1. Milky solution

  2. Bubble formation

  3. Solution turns red

  4. Brisk effervescence
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Two main observations during the reaction are:
(i) Brisk effervescence
(ii) Sodium acetate is formed

Chemical equation for the reaction is:

$2CH _3COOH + 2NaHCO _3 \to 2CH _3COONa + 2CO _2 + 2H _2O$


Option D is correct.
Multiple choice common laboratory equipments common laboratory apparatus and equipments laboratory equipments know about some common gases chemistry

What will happen if glass rod is made from reacting compound :

  1. It may cause certain accidents in the laboratory when exposed to certain chemicals

  2. It will interacts with the chemicals in the solution

  3. it will be corrosive to the atmosphere

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

If glass rod is made from reacting compound it will interact with the chemicals in the solution and contaminate the solution. It may cause certain accidents in the laboratory when exposed to certain chemicals. Also, it could be corrosive to atmosphere due to its reactive nature. 

Multiple choice chemistry substances in common use chemical from common salt compounds of carbon some useful compounds in everyday life

When treated with $conc. HCl, MnO _{2}$ yields a gas $(X)$ which further reacts with $Ca(OH) _{2}$ to generate a white solid $(Y)$. The solid $Y$ reacts with $dil. HCl$ to produce the same gas $X$. The solid $Y$ is :

  1. $CaO$
  2. $CaCl _{2}$
  3. $Ca(OCl)Cl$
  4. $CaCO _{3}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
X : Carbon dioxide              $CaCO _3+HCl  \rightarrow CaCl _2+ H _2O+CO _2$     
Y : Calcium Carbonate      $Ca(OH) _2 + CO _2 \rightarrow CaCO _3 + H _2O$
Z : $Ca(HCO _3) _2$                    $CaCO _3+H _2O+CO _2\rightarrow Ca(HCO _3) _2$
Multiple choice chemistry organic chemistry : some basic principles and techniques methods of purification of organic compounds methods of purification - organic compounds biochemical techniques

$ H _{2}O _{2}$ can be prepared by successive reactions:
$ 2NH _{4}HSO _{4}\rightarrow H _{2}+(NH _{4})^{2}S _{2}O _{8}$
$ (NH _{4}) _{2}S _{2}O _{8}+2H _{2}O \rightarrow  2NH _{4}HSO _{4}+ H _{2}O _{2}$
The first reaction is an electrolytic reaction and second is steam distillation. What amount of current would have to be used in first reaction to produce enough intermediate to yield 102 g pure $ H _{2}O _{2}$ per hour. Assume current efficiency 50 %.

  1. 643.33 A

  2. 321.67 A

  3. 160.83 A

  4. 1286.67 a
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

102 g H2O2 is 3 moles. The reaction produces 1 mole H2O2 per mole of (NH4)2S2O8. Electrolysis requires 2 moles of electrons per mole of persulfate. Total electrons = 6 moles. Faraday = 96500 C. Q = 6 * 96500 = 579,000 C. Current = Q/t = 579,000 / 3600 = 160.83 A. With 50% efficiency, I = 160.83 / 0.5 = 321.67 A.

Multiple choice chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

Limestone can be changed into slaked lime in two chemical reactions.
1 When limestone, $CaCO _{3}$, is heated it decomposes into lime, $CaO$.
2 Water is slowly dripped onto the cooled lime. The lime appears to expand and
steam is produced. Slaked lime, $Ca(OH) _{2}$, is formed.
Which row shows the correct description of each of the chemical reactions?

  1. Reaction $1$ - enodthermic, reaction $2$ - endothermic
  2. Reaction $1$ - enodthermic, reaction $2$ - exothermic
  3. Reaction $1$ - exothermic, reaction $2$ - endothermic
  4. Reaction $1$ - exothermic, reaction $2$ - exothermic
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Solution:- (B) Reaction $1$- endothermic, Reaction $2$- exothermic

When limestone is heated, the heat is absorbed and thus the reaction is endothermic and when steam is produced, the heat is released and thus the reaction is exothermic.

Multiple choice chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

In which of the following process heat is required?

  1. Mixing water and strong acids

  2. Some polymerisation reactions such as the setting of epoxy resin

  3. The setting of cement and concrete

  4. Combustion of fuels such as wood
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In combustion of fuels such as woods.

$C+O _2\longrightarrow CO _2+Heat$

Multiple choice chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

One of the following is an endothermic reaction. This is:

  1. combination of carbon and oxygen to form carbon monoxide.

  2. combination of nitrogen and oxygen to form nitrogen monoxide

  3. combination of glucose and oxygen to form carbon dioxide and water

  4. combination of zinc and hydrochloric acid to form zinc chloride and hydrogen.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
(A) This is an incomplete combustion reaction so energy will be released.
(B)Combination of nitrogen and oxygen to form Nitrogen Monoxide-
Heat is required for this process.
So $N _2 + O _2\rightarrow2NO-180.6KJ$ is an endothermic reaction.
(C) combination of glucose and oxygen to form carbon dioxide and water is a combustion reaction.So energy will be released.
(D)in a combination of zinc and hydrochloric acid to form zinc chloride and hydrogen heat is released.

so correct answer is  (B).
Multiple choice chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

During the reaction of some metals with dilute hydrochloric acid, the following observations were made. The temperature of the reaction mixture rises when aluminium (Al) is added mainly because :

                       

  1. Heat is evolved

  2. Due to the catalyst

  3. It is an endothermic reaction.

  4. It is an exothermic reaction.
Reveal answer Fill a bubble to check yourself
A,D Correct answer
Explanation

The temperature of the reaction mixture rises beacause, the following exothermic reaction takes place:

$2Al(s)  +  6HCl(aq)  \rightarrow   2AlCl _{3}(aq)  +  3H _{2}(g)  +  heat$