Atomic structure and periodic table
First ionisation energy definition
Energy required when 1 mole of gaseous atoms forms 1 mole of gaseous ions with a single charge
What is a dative covalent bond
When the shared pair of electrons in the covalent bond comes from only one of the bonding atoms
Disproportionation definition
An element of the same species is simultaneously oxidised and reduced
Trend of Group 7 melting/boiling point
Increase
More electrons = higher electron density
So larger London forces
Enthalpy change of formation
Enthalpy change when 1 mole of compound is formed from its elements under standard conditions
3 factors effecting ionisation energy
- Attraction of the nucleus
- Distance of electron from nucleus
- Shielding effect
Bond angle of Trigonal Pyramidal
107
Name this compound (you MIGHT need a number behind it)
NaNo3
Sodium Nitrate (V)
Observations for reacting NaCl with H2SO4
Steamy white fumes of HCl
Hess’s law states that
Enthalpy change for a reaction is independent of the route by which chemical reactions takes place
Relative isotopic mass definition ?
Mass of one atom of an isotope compared to 1/12 of the mass of one atom of carbon-12
Definition of metallic bonding
Strong electrostatic attraction between positively charged metal ions and the sea of delocalised electrons
Ideal gas equation + units
P = Pa
V = m^3
n = MoleR = -
T = K
Explain why thermal stability of group 2 carbonates decrease as you go down the group
- Cation gets bigger
- Less of a polarising effect
- So distorts the carbonate ion less
- So weakens the C-O bond less
Mean bond enthalpy definition
Energy needed to break covalent bond into gaseous atoms, averaged over different bonds
Why is there a decrease in first ionisation energy from Mg to Al
- Mg has a full 3s subshell while Al starts to fill the 3p subshell
- So easier to remove e- in outer shell of Al
Why can ionic substances dissolve in water?
- Negative ions are attracted to the delta positive hydrogens on the polar H2O molecules
- Positive ions are attracted to the delta negative oxygen on the polar H2O molecules
Colour changes in acid and alkali for:
Phenolphthalein
Methyl orange
Phenolphthalein :
Acid: Colourless Alkali: Pink
Methyl orange
Acid: Red Alkali: Yellow
Products of reaction Hot dilute NaOH solution with Cl2
NaClO3 + 3H2O + 5NaCl
2 errors in measuring enthalpy of combustion using calorimetry
• Energy losses from calorimeter
• Incomplete combustion of fuel
• Incomplete transfer of energy
• Evaporation of fuel after weighing
• Heat capacity of calorimeter not included
• Measurements not carried out under standard conditions as
H2O is gas, not liquid, in this experiment
Trend in boiling/ melting point of period 3
Na/Mg/Al/Si/P/S/Cl/Ar
Metallic- Na, Mg, Al so high
Covalent- Si so very high
Intermolecular forces P>S>Cl>Ar
Explain how London forces form
- Electrons are constantly moving
- Electron density fluctuates
- Temporary dipole forms
- Induces neighbouring molecules
Ionic equation for
acid + carbonate (Na2CO3) -> salt + water + CO2
2H(+) + CO3(2-) -> H2O + CO2
Explain how flame tests work
- Heat causes electron to move to a higher energy level
- Electron is unstable so it drops back down
- In doing so it emits energy in the form of visible light with wavelength of the observed colour
What is a heterogenous catalyst and how does it catalyse reactions
- A catalyst in a different phase from the reactants
- Reactants are adsorbed onto the surface of catalysts