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 chemistry study of the first element - hydrogen position of hydrogen in the periodic table hydrogen in periodic table trends in groups and periods

Hydrogen is :

  1. electropositive

  2. electronegative

  3. both electronpositive as well as electronegative

  4. neither electropositive nor electronegative
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Hydrogen is both electropositive as well as electronegative.
Like alkali metals, H has tendency to lose its one valency electron to form unipositive hydrogen ion $H^+$.
Hence, hydrogen is electropositive in nature.
Like halogens, hydrogen has tendency to gain one electron and form uninegative ion $H^-$.
Hence, hydrogen is electronegative in nature.

Multiple choice chemistry study of the first element - hydrogen position of hydrogen in the periodic table hydrogen in periodic table trends in groups and periods

Hydrogen behaves as a metal:

  1. at low temperature

  2. at low pressure

  3. at high temperature

  4. at high pressure
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Metallic hydrogen is a phase of hydrogen when it behaves as electrical conductor. At the high pressure of gigapascals hydrogen might exist as a liquid metal. Liquid metallic hydrogen is thought to be present in large amount in gravitationally compressed interiors of Jupiter and Saturn.

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

The reaction of zinc metal and $HCl$ produces which of the following?
i. $H _2(g)$
ii. $Cl _2(g)$
iii. $ZnCl _2(aq)$

  1. ii only

  2. iii only

  3. i and ii only

  4. i and iii only

  5. i, ii and iii
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Zn being an active metal it readily reacts HCl at room temperature.

$Zn+HCl\rightarrow ZnCl _{ 2 }+{ H } _{ 2 }$
It is a diplacement reation. 
Zinc displaces hydrogen from $HCl$.

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

A piece of zinc may be distinguished from a piece of magnesium by: 
(1) determining which conducts electricity
(2) determining which releases $H _2$ gas from a 1-molar hydrochloric acid solution
(3) measuring the density of each

  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
E Correct answer
Explanation

Both zinc and magnesium conduct electricity. Both zinc and magnesium reacts with hydrochloric acid to give hydrogen gas. They can be distinguished by measuring their densities.

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

The metal that cannot displace hydrogen from dilute hydrochlocric acid is 

  1. aluminium

  2. iron

  3. copper

  4. zinc

  5. magnesium
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Metals below hydrogen in the reactivity series, such as copper, cannot displace hydrogen from dilute acids. Aluminium, iron, zinc, and magnesium are all more reactive than hydrogen.

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

Which of the following is produced by the reaction of zinc metal, $Zn$ and hydrochloric acid, $HCl$?
I. $H _2(g)$
II. $Cl _2(g)$
III. $Zn^{2+}(aq)$

  1. II only

  2. III only

  3. I and II only

  4. I and III only

  5. I, II, and III
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$\displaystyle H _2$ and $\displaystyle Zn^{2+}$ is produced by the reaction of zinc metal, $Zn$, and hydrochloric acid, $HCl$.
$\displaystyle Zn + 2HCl  \rightarrow ZnCl _2 + H _2$

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

The addition of dilute $HCl$ to unknown metal produced a transparent gas. What is the likely identity of this gas?

  1. $Cl _{2}$
  2. $H _{2}$
  3. $O _{2}$
  4. $CO _{2}$
  5. $NO _{2}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Metals that come before hydrogen in the reactivity series form their corresponding chlorides when heated with HCl and liberate hydrogen gas.

Eg:
$Ca+2HCl\rightarrow { CaCl } _{ 2 }+{ H } _{ 2 }$

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  Reaction with dilute $HCl$  Reaction with dilute $HNO _3$
 Unknown metal #1  Dull gray solid with white oxide coating Dissolved with bubbles of clear gas   Dissolved with bubbles of clear gas
 Unknown metal #2  Solid; lustrous, smooth silver-gray surface  No reaction  Dissolved with bubbles of orange gas

Identify the orange gas produced on the addition of dilute $HN{O} _{3}$ to unknown metal #2.

  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
E Correct answer
Explanation

Silver has a lustrous smooth gray surface.

It reacts with $HNO _3$ as;
$3Ag+2{ HNO } _{ 3 }\rightarrow { 4AgNO } _{ 3 }+{ NO } _{ 2 }+{ H } _{ 2 }O$.
Thus the orange gas produced is $NO _2$.