Paper 1 Chemistry Flashcards
What is ionic bonding?
Ionic bonding is the electrostatic force attraction between oppositely charged ions formed by electrons transfer
What ion do metals form ?
What ion do non metals ?
Metal atoms lose electrons to form +ve ions. Non-metal atoms gain electrons to form -ve ions.
WHAT FACTOR INFLUENCE STRENGTH IONIC COMPOUND?
Ionic bonding is stronger and the melting points higher when the ions are smaller and/ or have higher charges.
WHAT STRUCTURE DOES IONIC CRYSTAL HAVE
Ionic crystals have the structure of giant lattices of ions
What happen to the sizes of negative and positive are formed
Positive ions are smaller compared to their atoms because it has one less shell of electrons and the ratio of protons to electrons has increased so there is greater net force on remaining electrons holding them more closely.
The negative ions formed from groups five to seven are larger than the corresponding atoms. The negative ion has more electrons than the corresponding atom but the same number of protons. So the pull of the nucleus is shared over more electrons and the attraction per electron is less, making the ion bigger.
What happen to the ionic radius when going down the group
Within a group the size of the ionic radii increases going down the group. This is because as one goes down the group the ions have more shells of electrons.
What is a covalent bond
A covalent bond is a shared pair of electrons
What is a dative covalent bond and what is the other name for it ?
A dative covalent bond forms when the shared pair of electrons in the covalent bond a dative covalent bond forms when the shared pair of electrons in the covalent bond
What is metallic bonding
Metallic bonding is the electrostatic force of attraction between the positive metal ions and the delocalised electrons
Three factor that affect strength metallic
Three factors that affect the strength of metallic
The three main factors that affect the strength of metallic bonding are:
- Charge of the ioned formed stronger attractive force between delocalised electron
- Number of delocalised electrons per atom (the outer shell electrons are delocalised) The more delocalised electrons the stronger the bond
- Size of ion. The smaller the ion, the stronger the bond.
What is electonegatvity ?
Name 4 most electronegatvity elements?
How happens to electronegatvity across the period
Electronegativity is the ability of an atom in a covalent bond in a molecule to attract electron Pair in a covalent bond to itself
F, O, N and Cl are the most electronegative atoms
Factors affecting electronegativity Electronegativity increases across a period as the number of protons increases and the atomic radius decreases because the electrons in the same shell are pulled in more.
What is a permanent dipole
What feature does molecule have to have cancel out pole bonds
Permanent dipole is polar covalent bond which has unequal distribution of electrons in the covalent bond producing dipoles and partial charges
A symmetrical molecules with all identical bond and no lone pair of electrons will not be polar even if the individual bonds are polar because the individual dipole on the molecule cancel out due to the symmetrical shape of the molecules and the molecules becomes non-polar
How van der waals force formed
What effect strength van der waals and how does that effect the boiling points
Vander waals force occur when electron distribution of original atoms / molecule changes and it induce new dipole in the atoms around it which will be attracted to the original atom /molecule .
Van der waals force strength increase with size and the number of electrons the molecule/atom resulting in higher melting and boiling point
How hydrogen bonds formed
What atoms can form hydrogen bonds
Hydrogen bonds occur in a compound that haves a hydrogen atom attached to one of three most electronegative atom (fluorine ,oxygen ,nitrogen )which must have lone pair of electron available
Nitrogen fluorine oxygen
Why does diamond have high melting point
what is the bonding shape of diamond
Why does water have lower density as solid then as a liquid
What cause graphite strucurly to have ability conduct electricity
Has four covalent per carbon atom resulting in many strong covalent bonds resulting high amount energy break the bonds
Tetrahedral
The molecules are held further apart than in liquid water and this explains the lower density of ice
Graphite has three covalent bonds per carbon atom in the layers 3 ,it has delocalised electron .
What is the enthalpy formation
Whats is the enthaly combustion
Describe the energy profile of a: exothermic reaction
and endothermic reaction
What is the enthalpy formation
Whats is the enthaly combustion
What is the definition of mean bond enthalpy
What is the equation to determine mean enthalpy bond energy
What does kc value great then 1 and then less 1
What are condition for system to be equilibrium
Four key features of equilibrium
What is le chatelier’s principle
How does equilibrium counteract these change to conditions :
Make it hotter
Make it cooler
Add more chemical A
Remove chemical A
Increase the pressure
Reduces the pressure
what is a electrochemical cell ?
what is a half cell?
electrochemical cell is made of two half cell and a salt bridge
a half cell is metal dipped into its ions or two aqueous ions
what is a salt bridge ?
what is salt bridge function ?
what are the requirement of a salt bridge
Salt bridge is used to connect up the circuit .
Allow the movement of ions and complete the circuit
Not be in contact with the electrode and not react with ions in the solutions
why is a high resistance volt meter used in electrochemical cell ?
why is a wire not used instead of a salt bridge?
what would happen if a current would flow in a electrochemical cell ?
what do solid vertical line represent in a cell diagram ?
what do double line represent in a cell diagram ?
the more/most [….] substance is next to the double line
The solid vertical line represents the boundary
between phases e.g. solid (electrode) and solution (electrolyte)
The double line represents the salt bridge
between the two half cells
oxidise
If a system does not include a metal that can act as an electrode, then a […] electrode must be used
and included in the cell diagram. It provides a conducting surface for […] transfer.
A platinum electrode is used because it is […]and can […].
platinum
electron
inert/unreactive
conduct electricity
The potential of all electrodes are measured by comparing
their potential to that of the standard hydrogen electrode.
The standard hydrogen electrode (SHE) is assigned the
potential of 0 volts.
| Fe3+ (aq), Fe2+ (aq) |Pt
The hydrogen electrode equilibrium is:
H2 ⇋(g) 2H+(aq) + 2e
In a cell diagram the hydrogen electrode is
represented by: Pt |H2 (g) | H+
(aq)
Components of a standard hydrogen electrode.
To make the electrode a standard reference electrode
some conditions apply:
1. Hydrogen gas at pressure of 100kPa
2. Solution containing the hydrogen ion at 1.0 mol dm-3
(solution is usually 1 mol dm-3 HCl)
3. Temperature at 298K
4. Platinum electrode
When an electrode system is connected to the
hydrogen electrode system, and standard conditions
apply the potential difference measured is called the
standard electrode potential, which are :
….KPa
….moldm-3
…K
As more +ve
increasing
tendency for
species on left to
reduce, and act
as oxidising
agents
As more -ve
increasing
tendency for
species on right
to oxidise, and
act as reducing
agents
The more negative half cell will
always […]
The more […] half cell will always
reduce
how do you calculate value of EMF
oxidised
positive
Ecell = Ereduced – Eoxdised
The most powerful reducing agents will be found at the most negative end of the series
on the right (i.e. the one with the lower oxidation number).
The most powerful oxidising agents will be found at the most positive end of the series on
the left (i.e. the one with the higher oxidation number).
Looking at cell reactions is a straight forward
application of le Chatelier. So increasing
concentration of ‘reactants’ would increase Ecell and
decreasing them would cause Ecell to decrease.
Most cells are exothermic in the spontaneous direction so applying Le Chatelier to a temperature rise to these
would result in a decrease in Ecell because the equilibrium reactions would shift backwards.
If the Ecell positive it indicates a reaction might occur. There is still a possibility, however, that the reaction will
not occur or will occur so slowly that effectively it does not happen.
If the reaction has a high activation energy the reaction will not occur
Electrochemical cells can be used as a commercial source of electrical energy
Cells can be non-rechargeable (irreversible), rechargeable and fuel cells.
