AQA AS Chemistry paper 2 Exam
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Define electronegativity. [1] - CORRECT ANSWER-The ability of an atom to attract electron
density from a covalent bond.
Define electron density. [1] - CORRECT ANSWER-How negative charge is distributed around an
atom or molecule.
Which is the most electronegative element? [1] - CORRECT ANSWER-Fluorine
,State three factors affecting electronegativity. [3] - CORRECT ANSWER-Nuclear charge
(higher= more electronegative)
Atomic radius (lower=more electronegative)
Shielding (lower=more electronegative)
Describe how a polar covalent bond forms. [3] - CORRECT ANSWER-A covalent bond between
atoms that differ in electronegativity.
The shared electrons are pulled closer to the more electronegative atom, making it slightly negative and
the other atom slightly positive.
May create a permanent dipole moment.
Why do not all polar bonds create a permanent dipole? [1] - CORRECT ANSWER-If a molecule
multiple polar bonds may cancel each other out (if they are working in opposite directions)
State the three different intermolecular forces, from weakest to strongest. [3] - CORRECT
ANSWER-Van der Waals > Permanent Dipole-Dipole > Hydrogen Bonding
Describe how permanent Dipole-Dipole forces form. [2] - CORRECT ANSWER-Occur between
any two molecules with dipole moments (not necessarily same molecule)
The end of a molecule with a slight positive charge is attracted to the end of another molecule with a
slight negative charge.
Describe how Van der Waals Forces form. [3] - CORRECT ANSWER-- Van der Waals forces act
between all atoms and molecules at all time.
- They work in addition to other intermolecular forces.
- The dipole moments are formed by the changing position of an electron cloud. The larger the electron
cloud the greater the dipole moment can be. Therefore larger molecules (higher Mr) have stronger Van
der Waals.
What criteria must be met for Hydrogen Bonds to form? [2]
, Why? - CORRECT ANSWER-- Molecules are needed in which a Hydrogen atom is bonded to
either Fluorine, Oxygen or Nitrogen
- Molecules are needed to have at least one lone pair of electrons. This can be the same type of
molecule as the first or different.
- Must have F-H, O-H or N-H as F, O & N are the most electronegative elements, and therefore form a
very strong dipole when bonded with H.
- When this dipole forms, the electron on H's outer shell is withdrawn very strongly- leaving the H atom
with almost no electron density and a very strong δ+ charge on the H.
- Any molecule with a lone pair will have strong attraction to the δ+ atom.
Define enthalpy change. - CORRECT ANSWER-A heat change measured at constant pressure
ΔH= enthalpy of products - enthalpy of reactants
What does standard conditions imply? [4] - CORRECT ANSWER-Pressure 100kPa
Temp 298K
Reactants and products in states that are normal under these conditions.
Any solutions conc 1.0moldm-3
Why are the physical states of the reactants and products important? [1] - CORRECT ANSWER-
They affect the enthalpy change of a reaction.
What occurs in an exothermic reaction? [2] - CORRECT ANSWER-- Loss/release of energy
- Negative value of ΔH
What occurs in an endothermic reaction? [2] - CORRECT ANSWER-- Gain of energy
- Positive value of ΔH
Define standard enthalpy of formation. [3] - CORRECT ANSWER-- Enthalpy change when one
mole of a substance is formed
Newest 2025 With Questions and
Verified Answers Graded A+|100%
Guarantee Pass!!!
Define electronegativity. [1] - CORRECT ANSWER-The ability of an atom to attract electron
density from a covalent bond.
Define electron density. [1] - CORRECT ANSWER-How negative charge is distributed around an
atom or molecule.
Which is the most electronegative element? [1] - CORRECT ANSWER-Fluorine
,State three factors affecting electronegativity. [3] - CORRECT ANSWER-Nuclear charge
(higher= more electronegative)
Atomic radius (lower=more electronegative)
Shielding (lower=more electronegative)
Describe how a polar covalent bond forms. [3] - CORRECT ANSWER-A covalent bond between
atoms that differ in electronegativity.
The shared electrons are pulled closer to the more electronegative atom, making it slightly negative and
the other atom slightly positive.
May create a permanent dipole moment.
Why do not all polar bonds create a permanent dipole? [1] - CORRECT ANSWER-If a molecule
multiple polar bonds may cancel each other out (if they are working in opposite directions)
State the three different intermolecular forces, from weakest to strongest. [3] - CORRECT
ANSWER-Van der Waals > Permanent Dipole-Dipole > Hydrogen Bonding
Describe how permanent Dipole-Dipole forces form. [2] - CORRECT ANSWER-Occur between
any two molecules with dipole moments (not necessarily same molecule)
The end of a molecule with a slight positive charge is attracted to the end of another molecule with a
slight negative charge.
Describe how Van der Waals Forces form. [3] - CORRECT ANSWER-- Van der Waals forces act
between all atoms and molecules at all time.
- They work in addition to other intermolecular forces.
- The dipole moments are formed by the changing position of an electron cloud. The larger the electron
cloud the greater the dipole moment can be. Therefore larger molecules (higher Mr) have stronger Van
der Waals.
What criteria must be met for Hydrogen Bonds to form? [2]
, Why? - CORRECT ANSWER-- Molecules are needed in which a Hydrogen atom is bonded to
either Fluorine, Oxygen or Nitrogen
- Molecules are needed to have at least one lone pair of electrons. This can be the same type of
molecule as the first or different.
- Must have F-H, O-H or N-H as F, O & N are the most electronegative elements, and therefore form a
very strong dipole when bonded with H.
- When this dipole forms, the electron on H's outer shell is withdrawn very strongly- leaving the H atom
with almost no electron density and a very strong δ+ charge on the H.
- Any molecule with a lone pair will have strong attraction to the δ+ atom.
Define enthalpy change. - CORRECT ANSWER-A heat change measured at constant pressure
ΔH= enthalpy of products - enthalpy of reactants
What does standard conditions imply? [4] - CORRECT ANSWER-Pressure 100kPa
Temp 298K
Reactants and products in states that are normal under these conditions.
Any solutions conc 1.0moldm-3
Why are the physical states of the reactants and products important? [1] - CORRECT ANSWER-
They affect the enthalpy change of a reaction.
What occurs in an exothermic reaction? [2] - CORRECT ANSWER-- Loss/release of energy
- Negative value of ΔH
What occurs in an endothermic reaction? [2] - CORRECT ANSWER-- Gain of energy
- Positive value of ΔH
Define standard enthalpy of formation. [3] - CORRECT ANSWER-- Enthalpy change when one
mole of a substance is formed
