Podcast
Questions and Answers
What is the combining capacity of an element known as?
What is the combining capacity of an element known as?
- Atomic number
- Molar mass
- Valency (correct)
- Ionic charge
What does the subscript '4' in OH4 signify in the context of chemical formulas?
What does the subscript '4' in OH4 signify in the context of chemical formulas?
- Number of valence shells
- Number of humans held by the octopus (correct)
- Number of atoms of each element
- Number of valence electrons
In chemical nomenclature, what is CaO called?
In chemical nomenclature, what is CaO called?
- Carbon oxide
- Copper oxide
- Calcium oxide (correct)
- Cadmium oxide
If an octopus represents an element with valency 2 and humans represent an element with valency 1, what would be the correct formula for the compound formed?
If an octopus represents an element with valency 2 and humans represent an element with valency 1, what would be the correct formula for the compound formed?
According to the information provided, how many arms do humans have in the analogy used to explain valency?
According to the information provided, how many arms do humans have in the analogy used to explain valency?
What is the combining capacity of an atom called?
What is the combining capacity of an atom called?
What is the formula of carbon tetrachloride?
What is the formula of carbon tetrachloride?
In magnesium chloride, why is the formula MgCl2?
In magnesium chloride, why is the formula MgCl2?
What is the formula for aluminum oxide?
What is the formula for aluminum oxide?
Why is the formula for calcium oxide CaO and not Ca2O2?
Why is the formula for calcium oxide CaO and not Ca2O2?
What is the formula for sodium nitrate?
What is the formula for sodium nitrate?
Why is the formula for calcium hydroxide Ca(OH)2?
Why is the formula for calcium hydroxide Ca(OH)2?
What is the valency of the aluminum ion in Al2(SO4)3?
What is the valency of the aluminum ion in Al2(SO4)3?
How many atoms are present in a single molecule of CaCl2?
How many atoms are present in a single molecule of CaCl2?
Which formula correctly represents sodium sulfide?
Which formula correctly represents sodium sulfide?
What is the molecular mass of HNO3?
What is the molecular mass of HNO3?
Which of the following compounds is a binary compound?
Which of the following compounds is a binary compound?
What is the correct chemical formula for magnesium hydroxide?
What is the correct chemical formula for magnesium hydroxide?
Study Notes
Ionic Compounds
- Calcium oxide is composed of calcium and oxygen in a 5:2 ratio by mass
- Magnesium sulphide is composed of magnesium and sulphur in a 3:4 ratio by mass
- Sodium chloride is composed of sodium and chlorine in a 23:35.5 ratio by mass
Chemical Formulae
- A chemical formula is a symbolic representation of a compound's composition
- Valency is the combining power of an element and can be used to find out how atoms combine to form a compound
- Valency can be thought of as the number of "hands" or "arms" an element has
Writing Chemical Formulae
- To write a chemical formula, the constituent elements and their valencies are written first
- Then, the valencies of the combining atoms are crossed over
- The formula for magnesium chloride is MgCl2, indicating two chloride ions (Cl-) for each magnesium ion (Mg2+)
Examples of Chemical Formulae
- The formula for carbon tetrachloride is not explicitly stated
- The formula for aluminium oxide is Al2O3
- The formula for hydrogen chloride is HCl
- The formula for calcium oxide is CaO
- The formula for sodium nitrate is NaNO3
- The formula for calcium hydroxide is Ca(OH)2
- The formula for aluminium sulphate is Al2(SO4)3
- The formula for calcium chloride is CaCl2
- The formula for potassium sulphate is K2SO4
- The formula for potassium nitrate is KNO3
- The formula for calcium carbonate is CaCO3
Molecular Mass and Mole Concept
- Molecular mass is the sum of the atomic masses of all the atoms in a molecule
- It is the relative mass of a molecule expressed in atomic mass units (u)
- The molecular mass of water (H2O) is the sum of the atomic masses of hydrogen and oxygen
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Description
This quiz covers writing chemical formulas for compounds by identifying the constituent elements and their valencies, followed by criss-crossing the valencies of the combining atoms. Examples include carbon tetrachloride and magnesium chloride.
