Which seven elements exist as diatomic molecules?

The seven elements that exist as diatomic molecules are hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, and iodine.

True or False? The molecular formula of water is HO 2 .

False . The molecular formula of water is H 2 O.

What does the subscript number in a molecular formula represent?

The subscript number in a molecular formula represents the number of atoms of that element in the molecule.

Define the term simple molecule.

A simple molecule is a molecule made up of a small number of atoms.

What is the molecular formula of ethene?

The molecular formula of ethene is C 2 H 4 .

True or False? Diatomic molecules always contain two atoms of different elements.

False . Diatomic molecules contain two atoms of the same element.

What does a molecular formula show?

A molecular formula shows the type and number of atoms in a molecule.

What is a chemical symbol?

A chemical symbol is a one or two-letter abbreviation used to represent an element in chemical formulas and equations.

Define empirical formula . (Extended tier only)

Empirical formula is the simplest whole number ratio of the atoms or ions present in a compound.

The molecular formula of propene is C 3 H 6 . What is the empirical formula? (Extended tier only)

The empirical formula of propene is CH 2 .

True or False? Organic molecules always have the same empirical and molecular formulae. (Extended tier only)

False . Organic molecules often have different empirical and molecular formulae.

What type of formula is used for ionic compounds ? (Extended tier only)

The formula of an ionic compound is always an empirical formula.

State the relationship between empirical and molecular formulae. (Extended tier only)

The molecular formula is a multiple of the empirical formula. It indicates the exact numbers of each atom in the compound.

True or False? Molecular formula shows the simplest whole number ratio of atoms in a molecule. (Extended tier only)

False. Empirical formula shows the simplest whole number ratio of atoms in a molecule.

State the formula of the ionic compound formed from: Fe 2+ Cl - (Extended tier only)

The formula of the ionic compound formed from Fe 2+ and Cl - is FeCl 2 .

State the formula of the ionic compound formed from: Li + Cl - (Extended tier only)

The formula of the ionic compound formed from Li + and Cl - is LiCl.

State the formula of the ionic compound formed from: Na + CO 3 2- (Extended tier only)

The formula of the ionic compound formed from Na + and CO 3 2- is Na 2 CO 3 .

True or False? A balanced chemical equation has the same number of atoms of each element on both sides.

True . A balanced chemical equation has the same number of atoms of each element on both sides, in accordance with the Law of Conservation of Mass.

What does a symbol equation use?

A symbol equation uses the formulae of the reactants and products to show what happens in a chemical reaction.

Products are the new substances which are on the right-hand side of the arrow in a chemical equation, formed by the reaction of reactants.

What are the constituent ions in the following? H 2 SO 4 NaOH KBr (Extended tier only)

The constituent ions are: H 2 SO 4 - two hydrogen ions (H + ) and one sulfate ion (SO 4 2- ) NaOH - one sodium ion (Na + ) and one hydroxide ion (OH - ) KBr - one potassium ion (K + ) and one bromide ion (Br - )

What numbers are missing to balance this equation? .....N 2 + .....H 2 ⇌ .....NH 3

The missing numbers to balance the equation are: N 2 + 3H 2 ⇌ 2NH 3

What are spectator ions ? (Extended tier only)

Spectator ions are ions which appear on both sides of an ionic equation and are eliminated from the final equation.

The relative atomic mass, A r , as the average mass of the isotopes of an element compared to 1/12th of the mass of an atom of carbon-12.

How is the relative atomic mass of an element determined?

The relative atomic mass of an element is found on the Periodic Table.

M r is the symbol for the relative formula mass and it refers to the total mass of the substance, which is the sum of the relative atomic masses of all atoms in a molecule.

How is the relative formula mass of a substance calculated?

To calculate the relative formula mass of a substance, you have to add up the relative atomic masses of all the atoms present in the formula.

True or False? Relative molecular mass applies to both ionic and covalent compounds

False . Relative molecular mass does not apply to ionic compounds.

What does the term molar mass mean?

Molar mass refers to the mass of one mole of a substance.

What is the relative formula mass of CuCO 3 ? ( A r 's: Ca = 40, C = 12, O = 16)

The relative formula mass of CuCO 3 is: 63.5 + 12 + (16 x 3) = 123.5

What is the relative molecular mass of C 5 H 5 N? ( A r 's: C = 12, H = 1, N = 14)

The relative molecular mass of C 5 H 5 N is: (12 x 5) + (1 x 5) + 14 = 79

What is the difference between relative molecular mass and relative formula mass?

The difference between relative molecular mass and relative formula mass is that relative moleculas mass only applies to covalent compounds. Relative formula mass applies to all compounds.

What is the relative molecular mass of NH 4 NO 3 ? ( A r 's: O = 16, H = 1, N = 14)

The relative molecular mass of NH 4 NO 3 is: 14 + (1 x 4) + 14 + (16 x 3) = 80

True or False? The relative formula mass of CaCO 3 is 100. (Ca=40, C=12, O=16)

True. The relative formula mass of CaCO 3 is = 40+12 +(16 x 3) = 100

IGCSEChemistryCambridge (CIE)Flashcards3. StoichiometryFormulae & Relative Masses

Formulae & Relative Masses (Cambridge (CIE) IGCSE Chemistry)

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Which seven elements exist as diatomic molecules?

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Cards in this collection (44)

Which seven elements exist as diatomic molecules?
The seven elements that exist as diatomic molecules are hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, and iodine.
True or False?
The molecular formula of water is HO₂.
False.
The molecular formula of water is H₂O.
What does the subscript number in a molecular formula represent?
The subscript number in a molecular formula represents the number of atoms of that element in the molecule.
Define the term simple molecule.
A simple molecule is a molecule made up of a small number of atoms.
What is the molecular formula of ethene?
The molecular formula of ethene is C₂H₄.
True or False?
Diatomic molecules always contain two atoms of different elements.
False.
Diatomic molecules contain two atoms of the same element.
What does a molecular formula show?
A molecular formula shows the type and number of atoms in a molecule.
What is a chemical symbol?
A chemical symbol is a one or two-letter abbreviation used to represent an element in chemical formulas and equations.
What does this dot and cross diagram represent?
The dot and cross diagram represents ammonia, NH₃, which consists of one nitrogen atom and three hydrogen atoms.
What does this displayed formula represent?
The displayed formula represents methane, CH₄, which consists of one carbon atom and four hydrogen atoms.
Define empirical formula. (Extended tier only)
Empirical formula is the simplest whole number ratio of the atoms or ions present in a compound.
The molecular formula of propene is C₃H₆. What is the empirical formula? (Extended tier only)
The empirical formula of propene is CH₂.
True or False?
Organic molecules always have the same empirical and molecular formulae. (Extended tier only)
False.
Organic molecules often have different empirical and molecular formulae.
What type of formula is used for ionic compounds? (Extended tier only)
The formula of an ionic compound is always an empirical formula.
State the relationship between empirical and molecular formulae. (Extended tier only)
The molecular formula is a multiple of the empirical formula.
It indicates the exact numbers of each atom in the compound.
True or False?
Molecular formula shows the simplest whole number ratio of atoms in a molecule. (Extended tier only)
False.
Empirical formula shows the simplest whole number ratio of atoms in a molecule.
State the formula of the ionic compound formed from:
- Fe²⁺
- Cl^-
(Extended tier only)
The formula of the ionic compound formed from Fe²⁺ and Cl^- is FeCl₂.
State the formula of the ionic compound formed from:
- Li⁺
- Cl^-
(Extended tier only)
The formula of the ionic compound formed from Li⁺ and Cl^- is LiCl.
What is the empirical formula of the following ionic compound?
(Extended tier only)
The empiticval formula of the ionic compound is AgF.
State the formula of the ionic compound formed from:
- Na⁺
- CO₃^2-
(Extended tier only)
The formula of the ionic compound formed from Na⁺ and CO₃^2- is Na₂CO₃.
True or False?
A balanced chemical equation has the same number of atoms of each element on both sides.
True.
A balanced chemical equation has the same number of atoms of each element on both sides, in accordance with the Law of Conservation of Mass.
Write the word equation for the reaction of silicon with oxygen to form silicon dioxide.
The word equation for the reaction of silicon with oxygen to form silicon dioxide is:
silicon + oxygen $\to$ silicon dioxide
What type of equation is this?
2Br^- + Cl₂ $\to$ Br₂ + 2Cl^-
2Br^- + Cl₂ $\to$ Br₂ + 2Cl^- is an ionic equation.
What does a symbol equation use?
A symbol equation uses the formulae of the reactants and products to show what happens in a chemical reaction.
What numbers are missing to balance this equation?
.....H₂O₂ $\to$ .....H₂O + ..... O₂
The missing numbers to balance the equation are:
2H₂O₂ $\to$ 2H₂O + O₂
What are products?
Products are the new substances which are on the right-hand side of the arrow in a chemical equation, formed by the reaction of reactants.
What are the constituent ions in the following?
- H₂SO₄
- NaOH
- KBr
(Extended tier only)
The constituent ions are:
- H₂SO₄ - two hydrogen ions (H⁺) and one sulfate ion (SO₄^2-)
- NaOH - one sodium ion (Na⁺) and one hydroxide ion (OH^-)
- KBr - one potassium ion (K⁺) and one bromide ion (Br^-)
Write the symbol equation for the reaction of magnesium with chlorine to form magnesium chloride.
The symbol equation for the reaction of magnesium with chlorine to form magnesium chloride is:
Mg + Cl₂ $\to$ MgCl₂
True or False?
The balanced symbol equation for the reaction of sodium with chlorine is:
Na + Cl₂ $\to$ NaCl₂
False.
The balanced symbol equation for the reaction of sodium with chlorine is:
2Na + Cl₂ $\to$ 2NaCl
What numbers are missing to balance this equation?
.....N₂ + .....H₂ ⇌ .....NH₃
The missing numbers to balance the equation are:
N₂ + 3H₂ ⇌ 2NH₃
What are spectator ions? (Extended tier only)
Spectator ions are ions which appear on both sides of an ionic equation and are eliminated from the final equation.
2KI + Br₂ $\to$ 2KBr + I₂
Why is this not an ionic equation? (Extended tier only)
2KI + Br₂ $\to$ 2KBr + I₂ is not an ionic equation because there are no ions.
Define A_r.
The relative atomic mass, A_r, as the average mass of the isotopes of an element compared to 1/12th of the mass of an atom of carbon-12.
How is the relative atomic mass of an element determined?
The relative atomic mass of an element is found on the Periodic Table.
${}_{9}^{19}F$
True or False?
The relative atomic mass of fluorine is 9.
${}_{9}^{19}F$
False.
The relative atomic mass of fluorine is 19.
The atomic number / number of protons in fluorine is 9.
Define M_r.
M_r is the symbol for the relative formula mass and it refers to the total mass of the substance, which is the sum of the relative atomic masses of all atoms in a molecule.
How is the relative formula mass of a substance calculated?
To calculate the relative formula mass of a substance, you have to add up the relative atomic masses of all the atoms present in the formula.
True or False?
Relative molecular mass applies to both ionic and covalent compounds
False.
Relative molecular mass does not apply to ionic compounds.
What does the term molar mass mean?
Molar mass refers to the mass of one mole of a substance.
What is the relative formula mass of CuCO₃?
(A_r's: Ca = 40, C = 12, O = 16)
The relative formula mass of CuCO₃ is:
63.5 + 12 + (16 x 3) = 123.5
What is the relative molecular mass of C₅H₅N?
(A_r's: C = 12, H = 1, N = 14)
The relative molecular mass of C₅H₅N is:
(12 x 5) + (1 x 5) + 14 = 79
What is the difference between relative molecular mass and relative formula mass?
The difference between relative molecular mass and relative formula mass is that relative moleculas mass only applies to covalent compounds.
Relative formula mass applies to all compounds.
What is the relative molecular mass of NH₄NO₃?
(A_r's: O = 16, H = 1, N = 14)
The relative molecular mass of NH₄NO₃ is:
14 + (1 x 4) + 14 + (16 x 3) = 80
True or False?
The relative formula mass of CaCO₃ is 100. (Ca=40, C=12, O=16)
True.
The relative formula mass of CaCO₃ is = 40+12 +(16 x 3) = 100

1. States of Matter

Solids, liquids & gases

2. Atoms, Elements & Compounds

3. Stoichiometry

4. Electrochemistry

5. Chemical Energetics

Exothermic & Endothermic Reactions

6. Chemical Reactions

7. Acids, Bases & Salts

8. The Periodic Table

9. Metals

10. Chemistry of the Environment

11. Organic Chemistry

12. Experimental Techniques & Chemical Analysis