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All questions of Language of Chemistry for Class 8 Exam

What is the first step in writing a chemical formula?
  • a)
    Write the symbols of the elements or radicals in the compound
  • b)
    Write the valency of each element
  • c)
    Simplify the formula
  • d)
    Count the number of atoms
Correct answer is option 'A'. Can you explain this answer?

Nishtha Iyer answered
Understanding the First Step in Writing a Chemical Formula
When writing a chemical formula for a compound, the initial and critical step is to write the symbols of the elements or radicals involved. This sets the foundation for the entire process.
Why Choose Option 'A'?
- Identification of Elements: The first step involves recognizing the elements that make up the compound. Each chemical element is represented by its unique symbol from the periodic table (e.g., H for hydrogen, O for oxygen).
- Building the Structure: By writing the symbols first, you can visualize the components of the compound. This is crucial for understanding how elements combine to form compounds.
Subsequent Steps in Formula Writing
After identifying the symbols, other steps follow:
- Writing Valencies: The next step would typically involve noting the valency of each element, which indicates how many bonds an atom can form.
- Combining Elements: You would then combine these symbols and valencies to create a balanced formula, ensuring that the total positive and negative charges are equal if ionic compounds are involved.
Conclusion
In summary, writing the symbols of the elements or radicals is essential as it serves as the starting point for constructing a chemical formula. This foundational step facilitates the understanding of how elements interact and combine, leading to the correct representation of compounds.

Which of the following is a characteristic of an endothermic reaction?
  • a)
    It always produces gas
  • b)
    It absorbs heat
  • c)
    It releases heat
  • d)
    It occurs at room temperature
Correct answer is option 'B'. Can you explain this answer?

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An endothermic reaction is characterized by the absorption of heat. Such reactions require energy input, which is often indicated in chemical equations by the presence of "Heat" on the reactant side.

Why might some elements have more than one valency?
  • a)
    They are always gases
  • b)
    They are unstable
  • c)
    They are radioactive
  • d)
    They can lose or gain different numbers of electrons
Correct answer is option 'D'. Can you explain this answer?

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Some elements have more than one valency because they can lose or gain different numbers of electrons when forming compounds. This property is essential in understanding how these elements react in various chemical contexts.

What does a radical refer to in chemistry?
  • a)
    A positively charged ion
  • b)
    An uncharged molecule
  • c)
    A group of different atoms acting as a single unit
  • d)
    A single atom
Correct answer is option 'C'. Can you explain this answer?

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A radical refers to a group of different atoms that act as a single unit with a positive or negative charge. Radicals play a crucial role in many chemical reactions, especially in organic chemistry.

What does the term "molecular formula" refer to?
  • a)
    The formula showing the actual number of atoms in a molecule
  • b)
    The chemical reaction process
  • c)
    The physical properties of a substance
  • d)
    The arrangement of atoms in a molecule
Correct answer is option 'A'. Can you explain this answer?

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The molecular formula refers to a representation that shows the actual number of each type of atom in a molecule. For example, C₆H₁₂O₆ indicates that a glucose molecule contains six carbon atoms, twelve hydrogen atoms, and six oxygen atoms.

When balancing the equation for methane burning in air, what is the balanced equation?
  • a)
    CH₄ + O₂ → CO₂ + H₂O
  • b)
    CH₄ + O₂ → 2CO₂ + H₂O
  • c)
    2CH₄ + O₂ → 2CO₂ + H₂O
  • d)
    CH₄ + 2O₂ → CO₂ + 2H₂O
Correct answer is option 'D'. Can you explain this answer?

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The balanced equation for methane burning in air is CH₄ + 2O₂ → CO₂ + 2H₂O. Balancing equations ensures that the number of each type of atom is the same on both sides, in accordance with the law of conservation of mass.

What is the primary purpose of using symbols and formulas in chemistry?
  • a)
    To represent elements, compounds, and reactions
  • b)
    To record laboratory observations
  • c)
    To create complex mathematical equations
  • d)
    To illustrate scientific theories
Correct answer is option 'A'. Can you explain this answer?

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Symbols and formulas in chemistry serve the essential purpose of representing elements, compounds, and reactions in a concise and understandable manner. They allow chemists to communicate complex ideas and chemical interactions clearly and efficiently.

Which of the following symbols indicates a solid state in a chemical equation?
  • a)
    (g)
  • b)
    (s)
  • c)
    (l)
  • d)
    (aq)
Correct answer is option 'B'. Can you explain this answer?

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The symbol (s) indicates a solid state in a chemical equation. This notation helps convey the physical state of each reactant and product, which is important for understanding the nature of the reaction.

Which of the following is a characteristic of a cation?
  • a)
    It has a negative charge
  • b)
    It is formed by losing electrons
  • c)
    It is always a gas
  • d)
    It is formed by gaining electrons
Correct answer is option 'B'. Can you explain this answer?

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A cation is formed when an atom or group of atoms loses electrons, resulting in a positive charge. Understanding cations is fundamental in the study of ionic compounds and their properties.

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