Physical Flashcards
Empirical Formula
The simplest whole number ratio of atoms (of each element) present in a compound
Formation of bleach
Cl2 + 2NaOH –> NaClO + NaCl + H2O
Electronegativity
The ability of an atom to attract electrons in a covalent bond
Explain why a molecule is polar
Net dipole
Dipoles do not cancel out
Molecule is non-symmetrical
Isotope
Atoms with different number of neutrons
Relative atomic mass
The weighted mean mass of an atom compared with 1/12th the mass of Carbon-12
Relative isotopic mass
The weighted mean mass of an isotope compared with 1/12th the mass of Carbon-12
Ionic lattice
Repeating pattern of oppositely charged ions
Covalent bond
Shared pair of electrons
Explain the different boiling points of NH3, F2 and Br2.
NH3 has hydrogen bonding
F2 and Br2 have London forces
Attraction is intermolecular for all 3
The London forces in Br2 are greater than in F2
Because bromine has more electrons than fluorine
hydrogen bonding in NH3 is stronger than London forces in F2
State and explain two anomalous properties of ice caused by hydrogen bonding
Ice is less dense than water; The molecules in ice are held apart by hydrogen bonds
Relatively high melting point
More energy is require to overcome hydrogen bonds because hydrogen bonds are stronger then other intermolecular bonds
State and explain two anomalous properties of ice caused by hydrogen bonding
Ice is less dense than water; The molecules in ice are held apart by hydrogen bonds
Ice has a relatively high melting point; Hydrogen bonds are stronger than other intermolecular
attractions or forces
Dative Bond
Both electrons have been donated by one atom
Metallic Bonding
attraction between the delocalised electrons and the positive ions
Ionic Bond
attraction between oppositely charged ions
Explain bond angles
Lone electron pairs repel more than bonded electron pairs
State and explain the trend in atomic radius from Li to F.
Decreases
Nuclear charge increases
Outer electrons experience similar shielding
Greater nuclear attraction on outer electrons
Conditions for formation of bleach
Cold, dilute NaOH
Calculating Bond enthalpy
Bonds broken (reactants) - Bonds Made (products)
The calculated value of ΔHc from this experiment is different from the value obtained from data books suggest reasons for the difference.
Heat loss Incomplete combustion Non-standard conditions Evaporation of alcohol/water Specific heat capacity of apparatus
Calculating enthalpy change of combustion
products - reactants
State the features of a dynamic equilibrium
closed system
Rate of the forward reaction is equal to the rate of the reverse reaction
concentration does not change
Explain this observation in terms of electrode potentials and equilibria. Include overall equations in your answer
Compare E values (which is more positive)
Equilibrium shift related to E values (More negative system shifts left, more positive system shifts right)
Full ionic equations of the system combinations
Explain why the student uses a large excess of methanol in this experiment (rates)
To ensure equilibrium is to the far right
To keep methanol zero order/constant
The enthalpy and entropy changes of a reaction both have a negative sign. Discuss how the feasibility of this reaction will change as the temperature increases
Reaction will become less feasible
Effect on ΔG - ΔG increases
Effect on TΔS - TΔS becomes more negative
2NO2(g) + O3(g) —> N2O5(g) + O2(g)
Explain why this reaction has a negative entropy change.
products have fewer gaseous moles
becomes more ordered
fewer ways of distributing energy
