Book cover for Objective Chemistry for Engineering and Medical Entrance Examinations

Objective Chemistry for Engineering and Medical Entrance Examinations

K Rama Rao

ISBN #9789332541771

1st Edition

2,463 Questions

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12,716 Students Helped

Homework Questions

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Summary
Learning Objectives
Key Concepts
Example Problems
Explanations
Common Mistakes

Summary

Hydrogen is a fundamental element with the unique ability to form various compounds through covalent, ionic, and hydrogen bonding. Its reactions, such as forming water and methane, are not only essential to basic chemical processes but also form the basis for important industrial applications like fuel cells and fertilizer production. Understanding hydrogen’s bonding capabilities and reaction mechanisms is crucial for exploring both theoretical chemistry and practical technology development.

Learning Objectives

1

Describe the properties of hydrogen and its role as the simplest element in the periodic table.

2

Explain the different types of chemical bonds (covalent, ionic, and hydrogen bonds) that hydrogen can form.

3

Analyze how hydrogen participates in key reactions such as the formation of water and methane.

4

Evaluate the industrial and practical applications of hydrogen compounds, including fuel cells and fertilizer production.

Key Concepts

CONCEPT

DEFINITION

Hydrogen

The lightest and most abundant element in the universe, known for its ability to form a variety of compounds through different types of chemical bonds.

Covalent Bond

A chemical bond formed when atoms share pairs of electrons, commonly seen in compounds like water (H2O) and methane (CH4).

Ionic Bond

A chemical bond formed through the electrostatic attraction between oppositely charged ions, which can involve hydrogen in compounds like certain acids.

Hydrogen Bond

A weak bond between a hydrogen atom and an electronegative atom, crucial in determining the properties of water and biological molecules.

Fuel Cells

Devices that convert the chemical energy of a fuel, such as hydrogen, directly into electricity through electrochemical reactions.

Fertilizer Production

An industrial process often involving hydrogen to synthesize compounds like ammonia, essential for the production of fertilizers.

Example Problems

Example 1

Which of the following statement is false? (1) Hydrogen can be placed in the halogen group because it forms hydrides like chlorides. (2) The best explanation for not placing hydrogen with the group of alkali metals or halogens is that the IP of $\mathrm{H}_{2}$ is too higher than alkali metal but too low than halogens. (3) The tendency of hydrogen to gain one electron to acquire He configuration resembles halogens. (4) Hydrogen molecules are diatomic and form $\mathrm{H}$ ions similar to halogens.

Example 2

The sum of the number of ncutrons and protons in one of the isotope of hydrogen is (1) 3 (2) 4 (3) 5 (4) 6

Example 3

Which of the following statements about tritium is falsc? (1) Tritium emits \gamma-rays. (2) Tritium is obtained by nuclcar reaction. (3) The disintegration product of tritium is ${ }_{2}^{3}$ IIc. (4) Its physical properties are different from thosc of dcuterium.

Example 4

Hydrogen shows (1) $+1$ oxidation state only (2) $-1$ oxidation state only (3) zero oxidation state only (4) $+1,-1$ and zero oxidation states

Example 5

Dcuteriun resembles hydrogen in chemical properties but reacts (1) slower than hydrogen (2) faster than hydrogen (3) more vigorously than hydrogen (4) just as hydrogen
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Step-by-Step Explanations

QUESTION

How does hydrogen combine with oxygen to form water (H2O)?

STEP-BY-STEP ANSWER:

Step 1: Identify the reactants. In this reaction, two molecules of hydrogen (H2) react with one molecule of oxygen (O2).
Step 2: Write the unbalanced chemical equation: H2 + O2 → H2O.
Step 3: Balance the equation by ensuring the number of hydrogen and oxygen atoms are equal on both sides. The balanced equation becomes 2H2 + O2 → 2H2O.
Step 4: Understand that each water molecule is formed through covalent bonding, where oxygen shares electrons with two hydrogen atoms.
Final Answer: Hydrogen reacts with oxygen in a 2:1 ratio to produce water, with the formation of covalent bonds between the atoms.

Formation of Water

QUESTION

How does hydrogen participate in the formation of methane (CH4)?

STEP-BY-STEP ANSWER:

Step 1: Identify the reactants involved. Methane consists of one carbon atom and four hydrogen atoms.
Step 2: Start with the basic reaction: C + H2 → CH4. Note that hydrogen is diatomic, so adjustments are needed.
Step 3: Write the balanced chemical equation: C + 2H2 → CH4, ensuring that the number of hydrogen atoms sums up to four.
Step 4: Recognize that the bond formation in methane is covalent, where the carbon atom shares electrons with four hydrogen atoms.
Final Answer: The formation of methane involves one carbon atom reacting with two molecules of diatomic hydrogen to form CH4 through covalent bonding.

Formation of Methane

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Common Mistakes

  • Confusing the types of bonds: Mistaking covalent bonds for hydrogen bonds or ionic bonds when discussing hydrogen's reactivity.
  • Incorrect balancing of chemical equations in reactions involving hydrogen, such as the formation of water or methane.
  • Overlooking the industrial relevance of hydrogen compounds, thereby underestimating their practical applications in energy and agriculture.
  • Misinterpreting the abundance and simplicity of hydrogen as an indicator of simple behavior; in reality, its bonding versatility leads to complex chemical behavior.