esq miss t Flashcards
Sodium fluoride contains sodium ions (Na) and fluoride ions (F-).
Na and F- have the same electron configuration.
Explain why a fluoride ion is larger than a sodium ion. (2)
-Fluoride ion has (two) fewer protons/lower nuclear charge
-Weaker attraction between nucleus and (outer) electrons
Explain, in terms of structure and bonding, why the melting point of sodium fluoride is high. (2)
-(Electrostatic) forces of attraction between oppositely charged ions/Na* and F-
-Lots of enerav needed to overcome break forces
Methoxymethane (CH3OCH3) is an isomer of ethanol.
In terms of the intermolecular forces involved, explain the difference in boiling points. (3)
-Hydrogen bonds (between ethanol molecules)
-permanent dipole-dipole OR van der Waals force between methovmethane molecules
-Hydrogen bonds are strongest intermolecular force
There are two lone pairs of electrons on the oxygen atom in a molecule of oxygen difluoride (OF2).
Explain how the lone pairs of electrons on the oxygen atom influence the bond angle in oxygen difluoride. (2)
-Lone pairs repel more than bond pairs
-angle will be lower
Silicon tetrafluoride (SiF4) is a tetrahedral molecule.
Deduce the type of intermolecular forces in SiF4
Explain how this type of intermolecular force arises and why no other type of intermolecular force exists in a sample of SiF4 (3)
-Van der Waals forces
-one molecule induces dipole in neighbouring/another/nearby molecule
-symmetrical molecule / dipoles cancel
OR
-no hydrogens bonded to F (N or O), therefore no hydrogen bonding
Explain how permanent dipole-dipole forces arise between hydrogen chloride molecules. (2)
-Difference in electronegativity leads to bond polarity
-(dipoles don’t cancel therefore the molecule has an overall permanent dipole) and there is an attraction between + on one molecule and 2- on another
Explain, in general terms, how a catalyst increases the rate of a reaction. (2)
-Provides an alternate pathway
-with lower activation energy
Explain, in general terms, how a catalyst increases the rate of a reaction. (2)
-Provides an alternate pathway
-with lower activation energy
Explain, in terms of collision theory, the effect of increasing the concentration of hydrogen peroxide on the rate of reaction. (2)
-More particles in a given volume
-Successful collisions are more frequent
Explain the effect that lowering the temperature would have on the rate of reaction. (2)
-Fewer particles will have the activation energy
-Fewer successful collisions in a given time
Explain the effect that lowering the temperature would have on the rate of reaction. (2)
-Fewer particles will have the activation energy
-Fewer successful collisions in a given time
Give the meaning of the terms saturated and hydrocarbon as applied to saturated hydrocarbons. (2)
Saturated: single bonds only
Hydrocarbon: only contains H and C
