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

Calcining at different temperatures produces magnesium oxide of different reactivity.

  1. True

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

Calcining at different temperatures produces magnesium oxide of different reactivity.

High temperatures (1500 – 2000 °C) diminish the available surface area and produces dead-burned (often called dead burnt) magnesia, an unreactive form used as a refractory.
Calcining temperatures (1000 – 1500 °C) produces hard-burned magnesia, which has limited reactivity and calcining at lower temperature, (700 – 1000 °C) produces light-burned magnesia, a reactive form, also known as caustic calcined magnesia.
Although some decomposition of the carbonate to oxide occurs at temperatures below 700 °C, the resulting material appears to reabsorb carbon dioxide from the air.

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

Which of the following is not a method of production of magnesium oxide?

  1. $ Mg+O _2 \rightarrow MgO $
  2. $MgCO _3\xrightarrow{\Delta}MgO+CO _2$
  3. $Mg(OH) _2\xrightarrow{\Delta}MgO+H _2O$

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

All of the above methods are used for the production of magnesium oxide.when magnesium is burnt in air magnesium oxide is produced. When magnesium carbonate is calcined magnesium oxide and carbon dioxide is produced. When magnesium hydroxide is calcined magnesium oxide and water is produced.

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

Give chemical name and nature (acidic or basic) of the ash formed by burning of a $Mg$ ribbon in the air? 

  1. magnesium chloride, acidic

  2. magnesium nitrite, basic

  3. magnesium oxide, acidic

  4. magnesium oxide, basic
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Option $(D)$ is correct.
Magnesium oxide is formed as ash by burning of $Mg$ ribbon in the air. This is an exothermic reaction.
$2Mg + O _2 \rightarrow 2MgO + \:energy$
Magnesium oxide is basic in nature as it reacts with water to form magnesium hydroxide which is a base.
Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

During the manufacturing of single superphosphate, excess silicon combines with acid to form:

  1. silicates

  2. silicic acid

  3. silanes

  4. hydride of silicon
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The reactions occurring  during the production of superphosphate are complex and are usually summarised as follows :

1. $Ca _5(PO _4) _3 F + 5H _2SO _4 \rightarrow 5CaSO _4 + 3H _3PO _4 + HF$
2. $Ca _5(PO _4) _3F + 7H _3 PO _4 + 5H _2O \rightarrow 5Ca(H _2PO _4) _2 H _2O + HF$
These reactions can be combined to give the overall equation :
$2Ca _5(PO _4) _3F + 7H _2SO _4 + 3 H _2O \rightarrow 7CaSO _4 + 3Ca(H _2PO _4) _2 H _2O + 2HF$
There are other reactions occurring at the same time. For example, virtually all the HF reacts with other silica minerals associated with the fluorapatite (silicates, quartz) to form silicon tetrafluoride. These gaseous emissions are recovered as hydroflusilicic acid $(H _2SiF _6)$ in the scrubbing system. Carbonates in the rock also react with sulfuric acid.

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

During the manufacturing of superphophates, fluorine and silicon impurities combines with water to form:

  1. silicic acid

  2. fluorosilicic acid

  3. silicon tetrafluoride

  4. form their oxides
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

During superphosphate production, silicon tetrafluoride (SiF4) is produced as a byproduct. When this reacts with water, it forms fluorosilicic acid (H2SiF6).

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

Silica reacts with magnesium to form a magnesium compound $X$. $X$ reacts with dilute $HCl$ and forms $Y$.

  1. $MgO$
  2. $MgSiO _3$
  3. $SiCl _4$
  4. $MgCl _2$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
As per the given question reactions are:

$SiO _2+2Mg\rightarrow 2MgO+Si$
silica                          $X$

Again,

$MgO+2HCl\rightarrow MgCl _2+H _2O$
 $X$                                $Y$
Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

The reaction between a metal and a diatomic gas leads to an ionic substance. What is the formula unit of the ionic compound produced when magnesium reacts with hydrogen gas?

  1. $MgO$
  2. $Mg(OH) _2$
  3. $MgH _{2}$

  4. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Magnesium react with hydrogen to produce magnesium hydride. chemical equations is as: 

$Mg + H _2 \rightarrow MgH _2$

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

When burned in open air, the magnesium gets hot enough to produce noticeable amounts of yellow magnesium nitride. Burning in a covered crucible that allows enough air in to support combustion will reduce the burning temperature, thus maximizing the production of the nitride.

  1. True

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

When magnesium burns, it is actually reacting with oxygen in the air and not with fire. Fire is what we call the heat and light produced when things burn Magnesium reacts with oxygen to make a compound called magnesium oxide. The bright light results because this reaction produces a lot of heat. so given statement is false

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

Magnesium oxide is produced by the calcination of magnesium phosphate or magnesium sulphate by the treating magnesium chloride with lime followed by heat.

  1. True

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

It is produced by the calcination of magnesium carbonate or magnesium hydroxide.The latter is obtained by the treatment of magnesium chloride solutions, typically seawater, with lime.

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

Magnesium on heating in air gives $(A)$ and $(B)$. On reaction with water $(B)$ gives colourless gas $(C)$. $(C)$ when passed through $CuSO _4$ solution gives a blue coloured solution $(D)$. The blue solution is:

  1. $MgO$
  2. $Mg _3N _2SO _3.H _2O$
  3. $NH _3$
  4. $[Cu(NH _3) _4]SO _4.H _2O$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Option $(D)$ is correct.

Magnesium on strong heating reacts with nitrogen of air.
$Mg + O _2 \rightarrow MgO  [A] + Mg _3N _2 [B]$
$Mg _3N _2 [B]  + H _2O \rightarrow Mg(OH) _2 + NH _3 [C]$
$ NH _3 + CuSO _4(aq) \rightarrow [Cu(NH _3) _4]SO _4.H _2O [D]$

Multiple choice chemistry matter in our surroundings diffusion in different states of matter properties of solids, liquid, and gas particle theory of matter

The chemical reaction between quicklime and water is characterised by:

  1. Evolution of hydrogen gas

  2. Suspension of slaked lime in water

  3. Change in temperature of mixture

  4. Change in colour of product
Reveal answer Fill a bubble to check yourself
B,C Correct answer
Explanation

Quicklime when added to water, it reacts with water chemically and form a suspension of slaked lime in water and produce heat energy. So it also results in an increase in temperature of the mixture.

$CaO+{ H } _{ 2 }O\rightarrow Ca{ (OH) } _{ 2 }+Heat$

Multiple choice chemistry planet earth acid deposition air and air pollution natural resources- air, water and land
The production of dihydrogen gas via water gas shift reaction,
 
$CO(g) + H _2O (g) \xrightarrow {\Delta/Catalyst} CO _2(g) + H _2(g).$

The $CO _2$ gas is removed by scrubbing with solution of 

  1. sodium arsenite

  2. calcium oxide

  3. sodium phosphate

  4. aluminium oxide
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The water-gas shift reaction (WGSR) describes  the reaction of carbon monoxide and water vapour to form carbon dioxide and hydrogen (the mixture of carbon monoxide and hydrogen is known as water gas)

$CO(g) + H _2O (g) \xrightarrow {\Delta/FeCrO _4} CO _2(g) + H _2(g).$

The carbondioxide obtained in the above reaction is removed by scrubbing with solution of sodium arsenite.

Multiple choice chemistry planet earth acid deposition air and air pollution natural resources- air, water and land

$SO _2$ is known to produce acid rain.

  1. True

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

$ {S}{O} _{2} $ produces acid rain. It reacts with atmospheric oxygen to produce $ {S}{O} _{3} $. This sulphur trioxide reacts with water to produce Sulphuric Acid. Thus acid rain is produced.

$ {2}{S}{O} _{2} $ ${+}$ $ {O} _{2} $ ${=}$ $ {2}{S}{O} _{3} $
$ {S}{O} _{3} $ ${+}$ $ {H} _{2}{O} $ ${=}$ $ {H} _{2}{S}{O} _{4}$

Multiple choice chemistry chemistry in everyday life metal oxides and non metal oxides reactions of acids and bases properties of acids and bases

Metallic oxides react with ............ to give salts and water, similar to the reaction of a/an ........... with an acid, metallic oxides are said to be basic oxides.

  1. bases, base

  2. acids, base

  3. acids, acid

  4. bases, acids
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Metallic oxides react with acids to give salts and water, similar to the reaction of a base with an acid, metallic oxides are said to be basic oxides.