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 reactivity series and electrochemistry reactivity series and displacement reactions chemical properties of metals chemical properties of metals and non metals

Reaction of hydrochloric acid with zinc oxide to form zinc chloride and water is a neutralization reaction.

  1. True

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

An acid neutralizes a base when they react with each other and respective salt and water are formed. Metal oxides are basic in nature. Thus, when an acid reacts with a metal oxide both neutralize each other. In this reaction, respective salt and water are formed.

Acid + Metal Oxide $\rightarrow$ Salt + Water

zinc oxide + hydrochloric acid $\rightarrow$ zinc chloride + water

$ 2HCl+ZnO \rightarrow  ZnCl _2+H _2O $

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

The following elements are listed in order of decreasing reactivity as they appear in the electrochemical series.

      $\displaystyle Na, Ca, Mg, Zn, Fe, H, Cu, Hg, Ag, Au$

Of the following, the element that does NOT react with hydrochloric acid to produce hydrogen gas is _______.

  1. $\displaystyle Zn$
  2. $\displaystyle Fe$
  3. $\displaystyle Hg$
  4. $\displaystyle Ca$
  5. $\displaystyle Mg$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Hg lies below hydrogen in the reactivity series. Therefore, Hg cannot replace hydrogen from $HCl$ and hydrogen gas is not released.

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

Which metals will displace hydrogen from both water and acids?

  1. $Li-Ca$
  2. $Mg-Pb$
  3. $Li-Na$
  4. $Cu-Ag$
Reveal answer Fill a bubble to check yourself
A,C Correct answer
Explanation

In nature, Oxidation occurs more than reduction. carbon, Sulfur, Nitrogen etc. gas converted to their oxides. This is oxidation. But, we never heard that their oxides converting to elements. So, $reduction$ is $less$.

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

What happens when a piece of aluminium metal is added to dilute hydrochloric acid?

  1. Aluminium displaces hydrogen

  2. Aluminium chloride is formed along with dilute hydrochloric acid

  3. Hydrogen gas is evolved

  4. No reaction
Reveal answer Fill a bubble to check yourself
A,C Correct answer
Explanation

On adding aluminium(Al) to dilute hydrochloric acid(HCl), the following displacement reaction takes place:
$2Al(s)  +  6HCl(aq)  \rightarrow   2AlCl _{3}(aq)  +  3H _{2}(g)$
Aluminium being more reactive than hydrogen, displaces the latter in hydrochloric acid $(HCl)$ to form aluminium chloride($AlCl _{3}$).

Multiple choice chemistry water drying and dehydrating agents hydrolysis of salts and the ph of their solutions chemical equilibrium and acids-bases

Does $Mg(OH) _2$ react with sodium hydroxide?

  1. True

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

A universal indicator is a pH indicator composed of a solution of several compounds that exhibits smooth colour changes over a pH value range from 1-14 to indicate the acidity or alkalinity of solutions. Two basic hydroxides do not react with each other as these are bases but not alkali.

Multiple choice chemistry water drying and dehydrating agents hydrolysis of salts and the ph of their solutions chemical equilibrium and acids-bases

What are the products formed when an aqueous solution of magnesium bicarbonate is boiled?

  1. $MgCO _3,\, H _2O,\, CO _2$
  2. $Mg(HCO _3) _2,\, H _2O$
  3. $Mg(OH) _2,\, H _2O$
  4. $Mg,\, CO _2,\, H _2O$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When magnesium bicarbonate is boiled $MgCO _3, H _2O$ and $CO _2$ are formed. A small amount of $Mg(OH) _2$ is also formed.

Reaction: $Mg(HCO _ 3) _2\xrightarrow[\Delta]{} MgCO _ 3+H _ 2O+CO _ 2+Mg(OH) _ 2$

Multiple choice chemistry water drying and dehydrating agents hydrolysis of salts and the ph of their solutions chemical equilibrium and acids-bases

When hydrated $MgCl _2.\, 6H _2O$ is strongly heated:

  1. $MgO$ is formed
  2. $Mg(OH) _2$ is formed
  3. $Mg(OH)Cl$ is formed
  4. Ahydrous $MgCl _2$ is formed
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Magnesium hydrochloride is hygroscopic in nature and it loses its water molecules with the formation of magnesium oxide. When mixed with hydrated magnesium oxide, magnesium chloride forms a hard material called Sorel cement.

Multiple choice chemistry water drying and dehydrating agents hydrolysis of salts and the ph of their solutions chemical equilibrium and acids-bases

During the preparation of hydrogen chloride gas on a humid day, the gas is usually passed through two guard tube containing calcium chloride. The role of calcium chloride in the guard tube is:

  1. it absorbs the evolved gas

  2. it moisten the gas

  3. it absorbs moisture from the gas
  4. it absorbs $Cl^-$ ions form the gas evolved
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Calcium chloride is hygroscopic in nature and its anhydrous salt is deliquescent and it can accumulate enough water in its crystal lattice to form a solution. It is used as a drying agent to absorb moisture from the environment.

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

When hydrogen and oxygen combine to form water, they form:

  1. an unstable compound

  2. a stable mixture

  3. an unstable mixture

  4. an extremely stable compound
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

When hydrogen and oxygen combine to form water, they form water an extremely stable compound. We can say water is a stable compound because tremendous energy is released is a signal that hydrogen and oxygen are very eager to become water or in another way it is very hard to break water molecules apart into its components.

$2H _2+O _2\longrightarrow 2H _2O$