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Questions and Answers
What is the correct chemical symbol for sodium?
What is the correct chemical symbol for sodium?
- Na (correct)
- Sd
- S
- So
The symbol for cobalt is CO.
The symbol for cobalt is CO.
False (B)
What is the latest abbreviation for atomic mass unit as recommended by IUPAC?
What is the latest abbreviation for atomic mass unit as recommended by IUPAC?
u
The chemical symbol for chlorine is ______.
The chemical symbol for chlorine is ______.
Match the following elements with their symbols:
Match the following elements with their symbols:
What is the formula for magnesium chloride?
What is the formula for magnesium chloride?
The bracket is required when indicating one polyatomic ion in a chemical formula.
The bracket is required when indicating one polyatomic ion in a chemical formula.
What is the formula for sodium nitrate?
What is the formula for sodium nitrate?
In the compound magnesium chloride, there are ___ chloride ions for each magnesium ion.
In the compound magnesium chloride, there are ___ chloride ions for each magnesium ion.
Match the following compounds with their formulas:
Match the following compounds with their formulas:
How do you simplify the formula Ca2O2?
How do you simplify the formula Ca2O2?
In binary compounds, the charges on the ions must balance each other.
In binary compounds, the charges on the ions must balance each other.
The formula for hydrogen chloride is ___ .
The formula for hydrogen chloride is ___ .
Who postulated the idea of dividing matter into smaller particles known as Parmanu?
Who postulated the idea of dividing matter into smaller particles known as Parmanu?
The concept of indivisible particles called atoms was introduced by Paul Dirac.
The concept of indivisible particles called atoms was introduced by Paul Dirac.
What does the term 'atom' mean?
What does the term 'atom' mean?
According to the ancient philosophers of India, if matter is divided, we will eventually reach the smallest particles called __________.
According to the ancient philosophers of India, if matter is divided, we will eventually reach the smallest particles called __________.
Match the following philosophers with their contributions:
Match the following philosophers with their contributions:
What was the main focus of ancient Indian and Greek philosophers regarding matter?
What was the main focus of ancient Indian and Greek philosophers regarding matter?
The law of conservation of mass states that mass can be created during a chemical reaction.
The law of conservation of mass states that mass can be created during a chemical reaction.
The ancient philosopher who suggested that matter cannot be divided further is __________.
The ancient philosopher who suggested that matter cannot be divided further is __________.
What is the correct chemical formula for calcium hydroxide?
What is the correct chemical formula for calcium hydroxide?
The molecular mass of water is equal to 18 atomic mass units.
The molecular mass of water is equal to 18 atomic mass units.
How many hydrogen atoms are present in one molecule of ammonium sulfate, (NH4)2SO4?
How many hydrogen atoms are present in one molecule of ammonium sulfate, (NH4)2SO4?
The molecular mass of nitric acid (HNO3) is ____ u.
The molecular mass of nitric acid (HNO3) is ____ u.
Which of the following describes the concept of molecular mass?
Which of the following describes the concept of molecular mass?
In the molecular formula Na2CO3, brackets are required for the carbonate ion.
In the molecular formula Na2CO3, brackets are required for the carbonate ion.
Calculate the molecular mass of calcium hydroxide, Ca(OH)2.
Calculate the molecular mass of calcium hydroxide, Ca(OH)2.
Match the chemical formulas on the left with their common names on the right:
Match the chemical formulas on the left with their common names on the right:
What is the smallest particle of an element that cannot usually exist independently?
What is the smallest particle of an element that cannot usually exist independently?
A molecule can exist independently and shows all the properties of the substance.
A molecule can exist independently and shows all the properties of the substance.
What is a polyatomic ion?
What is a polyatomic ion?
The chemical formula of a compound shows its constituent elements and the number of _____ of each combining element.
The chemical formula of a compound shows its constituent elements and the number of _____ of each combining element.
Match the following compounds with their chemical formulae:
Match the following compounds with their chemical formulae:
When 3.0 g of carbon is burned in 8.00 g of oxygen, which law of chemical combination is demonstrated?
When 3.0 g of carbon is burned in 8.00 g of oxygen, which law of chemical combination is demonstrated?
In ionic compounds, the chemical formula is determined by the mass of the ions present.
In ionic compounds, the chemical formula is determined by the mass of the ions present.
List two examples of polyatomic ions.
List two examples of polyatomic ions.
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Study Notes
Chemical Formulas and Ionic Compounds
- Magnesium chloride has the chemical formula MgCl2, indicating two chloride ions per magnesium ion.
- Chemical formulas are written by combining the symbols of the elements and their respective valencies.
- When multiple identical polyatomic ions are present, their formula is enclosed in brackets with a subscript indicating quantity.
Binary Compounds
- Binary compounds consist of two different elements.
- Valencies can be crossed over to determine the formula; for example, calcium oxide simplifies from Ca2O2 to CaO.
Notable Examples
- Hydrogen chloride: HCl
- Aluminum oxide: Al2O3
- Calcium hydroxide: Ca(OH)2, depicting two hydroxyl groups.
- Sodium nitrate: NaNO3
- Sodium carbonate: Na2CO3
- Ammonium sulfate: (NH4)2SO4
Molecular Mass
- Molecular mass refers to the sum of atomic masses of all atoms in a molecule, expressed in atomic mass units (u).
- Example calculations show water (H2O) has a molecular mass of 18 u; HNO3 totals 63 u.
Historical Context of Matter
- Ancient philosophers theorized about the divisibility of matter; the concept of 'Parmanu' by Maharishi Kanad represents the smallest particles.
- The term "atom" was coined by Democritus, meaning "indivisible".
Modern Chemistry Foundations
- The law of conservation of mass states that mass remains constant during a chemical reaction.
- Chemical formulas identify both the elements and their quantities in a compound.
Polyatomic Ions
- Polyatomic ions are clusters of atoms that carry a fixed charge.
- Formulae include brackets when multiple identical units are present; e.g., in calcium hydroxide, brackets indicate two hydroxyl ions.
Exercises on Understanding Chemistry
- Weight composition and mass calculations in chemical reactions exemplify practical applications of the laws of chemical combinations.
Group Activity Suggestion
- Create a fun placard game to reinforce knowledge of the symbols, valencies, and formulae of elements.
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