Chemistry

Chemical Reactions and Processes

571 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

Barium oxide + hydrochloric acid --> ______ + ______

  1. barium chloride + water

  2. barium chloride + hydrogen

  3. barium sulfate + water

  4. barium sulfate + hydrogen
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Barium oxide (a metal oxide) reacts with hydrochloric acid to form barium chloride (a salt) and water.

Multiple choice

Copper + Sulfuric acid --> ______ + Hydrogen

  1. copper sulfate

  2. copper nitrate

  3. copper sulfuric

  4. sulfur culpate
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Copper reacts with sulfuric acid to form copper sulfate and hydrogen gas. Note that copper is less reactive, but the chemical equation follows the standard metal-acid pattern.

Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

Magnesium metal is heated to redness in the presence of nitrogen and on cooling water is added. The gas evolved is:

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

The gas evolved is $NH _{3}$.

When magensium is heated to redness in the presence of nitrogen, it forms magnesium nitride.
$ 3Mg + N _{2} \rightarrow Mg _{3}N _{2}$

This magnesium nitride when reacts with water forms ammonia gas.
$Mg _{3}N _{2} + 6H _{2}O \rightarrow3Mg(OH) _{2} + 2NH _{3}$

Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

A metal $M$ readily forms its sulphate $MSO _{4}$ which is water soluble. It forms its oxide $MO$ which becomes inert on heating. It forms an insoluble hydroxide $M(OH) _{2}$ which is soluble in $NaOH$ solution. Then M is:

  1. $Mg$
  2. $Ba$
  3. $Ca$
  4. $Be$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In the periodic table, on moving down, water solubility of alkaline earth metal decreases. Oxides and hydroxides of alkaline earth metal are basic except Be which is amphoteric.
Hence the metal M is Be.
conclusion: hence the option (D) is correct.

Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

When heated in steam, Mg burns brilliantly producing:

  1. $Mg(OH) _2$
  2. $MgO and H _2$
  3. $MgO and O _2$
  4. $MgO and O _3$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Magnesium burns in steam to produce white magnesium oxide and hydrogen gas. Very clean magnesium ribbon has a very slight reaction with cold water. After several minutes, some bubbles of hydrogen form on its surface, and the coil ofmagnesium ribbon usually floats to the surface.

The reaction occurs is,
$Mg+H _2O (g) \rightarrow MgO +H _2$

Hence option B is correct answer.

Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

The reaction between marble and dilute $H _2SO _4$ is not used to prepare carbon dioxide for laboratory purpose.
Answer whether the above statement is true or false.

  1. True

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

Insoluble $CaSO _4$ is formed which deposits on the surface of marble and prevent the further action of dilute $H _2SO _4$, so the evolution of $CO _ 2$ ceases after some time.

Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

How is Magnesium sulphate produced from Magnesium?

  1. $Mg$ $+$ $H _2SO _4$
  2. $Mg$ $+$ $SO _2$
  3. $Mg$ $+$ $SO _3$
  4. $Mg$ $+$ $H _2SO _3$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When $Mg$ is dissolved in dilute Sulphuric acid, an aqueous solution of Magnesium Sulphate is obtained. The reaction can be represented as-
$Mg$ $+$ $H _2SO _4$ $=$ $MgSO _4$ $+$ $H _2$
This colourless aqueous solution when evaporates, colorless crystals of $MgSO _4.7H _2O$ are formed.

Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

How does Magnesium Oxide give Magnesium Sulphate?

  1. $MgO$ $+$ $H _2SO _3$
  2. $MgO$ $+$ $H _2SO _4$
  3. $MgO$ $+$ $SO _2$
  4. $MgO$ $+$ $SO _3$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When magnesium oxide is dissolved in dilute sulphuric acid, it forms colorless aqueous solution of Magnesium Sulphate. The balanced equation can be written as-
$MgO$ $+$ $H _2SO _4$ $=$ $MgSO _4$ $+$ $H _2O$
This aqueous solution when evaporates and crystallizes, colorless crystals of Epsom salt are obtained.

Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

What is the end product when $MgCl _2 \cdot 6H _2O$  is strongly heated?

  1. $MgO$
  2. $MgCl _2$
  3. $Mg _2OCl _2$

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

When $MgCl _2 \cdot 6H _2O$  is strongly heated, the end product is $MgO$.
$MgCl _2 \cdot 6H _2O \xrightarrow {heat} MgCl _2 \cdot 2H _2O \xrightarrow {heat}  Mg _2OCl _2 \xrightarrow {heat}  MgO $
The byproducts obtained are $H _2O$, $HCl$ and $Cl _2$.

Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

What happens when $MgCl _2 \cdot 6H _2O$ is heated?

  1. $MgCl _2 \cdot 2H _2O$ is obtained
  2. Anhydrous $MgCl _2 $ is obtained
  3. $MgCl _2 \cdot 4H _2O$ is obtained

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

When $MgCl _2 \cdot 6H _2O$ is heated, $MgCl _2 \cdot 4H _2O$ is obtained. Four molecules of water (per molecule of hexahydrate) are lost. This is dehydration.

Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

Reaction of magnesium with air is:

  1. endothermic reaction

  2. reversible reaction

  3. exothermic reaction

  4. substitution reaction
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Option $(C)$ is correct.

The reaction of magnesium with air is an exothermic reaction as magnesium burns with dazzling brilliance in the air forming white shiny magnesium oxide with the evolution of a lot of heat.
$2Mg + O _2 \rightarrow 2MgO + heat$