Questions and Answers
What was the significance of Antoine L.Lavoisier's work in the field of chemical sciences?
What is the reason for putting a cork on the mouth of the flask in the experiment?
What can be concluded from the experiment shown in Fig. 3.1?
What was the occupation of John Dalton's father?
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What is the significance of weighing the flask with its contents before and after the reaction?
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Who is credited with calling the indivisible particles 'atoms'?
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What was the age of John Dalton when he became a teacher?
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What is the significance of tilting and swirling the flask in the experiment?
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What happened to John Dalton 7 years after he became a teacher?
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What is the ratio of mass of elements in a chemical substance according to the law of constant proportions?
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Who is credited with providing the basic theory about the nature of matter?
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What is the smallest unit of matter according to Dalton's atomic theory?
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What is the number of whole numbers in which atoms combine to form compounds?
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What is the characteristic of atoms of a given element according to Dalton's atomic theory?
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What is the difference between atoms of different elements according to Dalton's atomic theory?
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What is the purpose of Dalton's atomic theory?
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What is the total mass of products formed in the reaction between sodium carbonate and acetic acid?
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What is the name of the law that states elements are always present in a definite ratio by mass?
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What is the term used to describe the number of atoms constituting a molecule?
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What type of molecule has a simple structure with a very large and indefinite number of atoms bonded together?
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What is the ratio of oxygen to nitrogen in a molecule of ammonia (NH3)?
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What is the molecular formula for ozone?
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What is the term used to describe the ratio of atoms present in molecules?
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What type of molecule consists of two atoms of oxygen?
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What is the molecular formula for carbon dioxide?
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What type of elements do not have a simple structure but consist of a very large and indefinite number of atoms bonded together?
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What is the purpose of Table 3.2?
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What is the formula of sodium carbonate?
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What is the formula of ammonium sulphate?
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What is the molecular mass of water (H2O)?
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What is the formula unit mass of a substance?
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What is the molecular mass of HNO3?
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How is the formula unit mass of a substance calculated?
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What is the purpose of calculating the formula unit mass of a substance?
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What is the formula of sodium oxide?
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What is the formula of aluminium chloride?
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What is the atomicity of oxygen?
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What is the ratio by number of atoms for water?
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What is the atomic mass of helium?
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What is an ion?
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What is the atomicity of phosphorus?
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What is the atomic mass of oxygen?
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What is the atomicity of chlorine?
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What is the characteristic of compounds composed of metals and non-metals?
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What is the atomicity of hydrogen?
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Study Notes
Democritus and the Concept of Atoms
- Democritus introduced the idea of indivisible particles called atoms.
- He believed that atoms are the building blocks of matter and cannot be divided further.
Laws of Chemical Combination
- By the end of the 18th century, scientists recognized the difference between elements and compounds.
- Antoine Lavoisier laid the foundation of chemical sciences by establishing two important laws of chemical combination.
- A chemical reaction occurs when solutions X and Y are mixed in a conical flask.
- The mass of the flask and its contents remains the same before and after the reaction, illustrating the law of conservation of mass.
- John Dalton's law of definite proportions states that elements in a chemical substance are always present in definite proportions by mass, regardless of the method or source.
Dalton's Atomic Theory
- John Dalton introduced the concept of atoms as the smallest particles of matter.
- He said that atoms are indivisible and cannot be created or destroyed in a chemical reaction.
- Dalton's atomic theory explains the law of constant proportions.
- Atoms of a given element are identical in mass and chemical properties.
- Atoms of different elements have different masses and chemical properties.
- Atoms combine in the ratio of small whole numbers to form compounds.
Atomicity of Elements
- Atomicity refers to the number of atoms constituting a molecule.
- Metals and some non-metals, such as carbon, do not have a simple structure but consist of a large and indefinite number of atoms bonded together.
- Examples of atomicity include:
- Diatomic molecules: oxygen (O2), hydrogen (H2), chlorine (Cl2)
- Monoatomic elements: argon, helium
- Tetra-atomic element: phosphorus
- Poly-atomic element: sulphur
Ions and Compounds
- Ions are charged species that can consist of a single charged atom or a group of atoms with a net charge.
- Ions can be negatively or positively charged.
- Compounds composed of metals and non-metals contain ions.
Formulae and Molecular Mass
- Formulae represent the composition of a compound in terms of its constituent elements.
- Examples of formulae include:
- Sodium carbonate: Na2CO3
- Ammonium sulphate: (NH4)2SO4
- Molecular mass is calculated by summing the atomic masses of all atoms in a molecule.
- Formula unit mass is calculated in the same manner as molecular mass.
Chapter Activities and Questions
- Activity 3.2 involves finding the ratio by number of atoms of elements in molecules.
- Questions include:
- Writing formulae for compounds represented by their names.
- Calculating molecular mass and formula unit mass.
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Description
This quiz is about Democritus' concept of atomic structure and an experiment involving solutions X and Y.