Module 3 Flashcards
Define first ionisation energy
the energy required to remove one electron from each atom in one mole of gaseous atoms of an element
Which factors affect ionisation energy across a Period?
Atomic Radius Decreases Nuclear Charge Increases Electron Shielding Remains Similar (Greater Charge Density) First Ionisation Energy Increases
Which factors affect ionisation energy down a Group?
Atomic Radius Increases
Nuclear Attraction Decreases
Electron Shielding Increases
First Ionisation Energy Decreases
Describe Metallic Bonding
The electrostatic attraction between positive metal ions and a sea of delocalised electrons
What is the pattern in melting points across the period table?
It increases from groups 1 to 14 (giant structures) and then decreases from groups 15 to 18 (simple molecules with IM-forces) ((After Si))
Why does the reactivity of group 2 elements increase down the group?
Group 2 elements react by losing electrons, further down the group the attraction between the outer-electron and the nucleus decreases
Describe the trend in the solubility of group 2 hydroxides?
As you descend the group, solubility of the group 2 hydroxide increases and hence, pH increases also
How does the reactivity of the Halogens change down the group?
It decreases, because the atomic radius is increasing and so is the shielding
What is a disproportionation reaction?
One where the same species is both oxidised and reduced
State a concern associated with putting chloride ions in the water to sterilise it
It might react with alkanes, to form carcinogenic haloalkanes
What is the correct order to carry out the qualitative negative ion tests?
1) Carbonate (add nitric acid, makes carbon dioxide)
2) Sulphate (add barium nitrate, makes a white ppt)
3) Halide (add silver nitrate, makes coloured ppts)
(‘4’) add ammonia to coloured ppts, only iodine will not dissolve)
Define enthalpy change of reaction
the enthalpy change that accompanies a reaction in the molar quantities in the equation
Define enthalpy change of formation
the enthalpy change that accompanies the formation of one mole of a compound from its elements
Define enthalpy change of combustion
the enthalpy change that takes place when one mole of a substance reacts completely with oxygen
Define enthalpy change of neutralisation
the enthalpy change that accompanies the reaction of an acid by a base to produce one mole of water
What is the equation for energy change (involving specific heat capacity)?
q=mc Δt
What can cause inaccuracies in the experimental enthalpy change value compared to the standard one?
It was measured in non-standard conditions
Incomplete combustion occurred
Heat was lost (transferred) to the surroundings
What is the bond enthalpy of a bond?
The energy required to break one mole of the bond in its gaseous state
What factors can affect the rate of a reaction?
Concentration / Pressure
Temperature
Use of a catalyst
Surface area (if solid)
What defines whether or not a collision is effective in a reaction?
If it has or not collided in the correct orientation, and with enough energy, to actually react
What are the key features of catalysts?
They lower activation energy, without undergoing any permanent change themselves (always regenerated)
What is the difference between Homogenous and Heterogeneous catalysts?
Homogenous catalysts are in the same state as the reactants, and often form intermediates. Heterogeneous catalysts are in a different state to the reactants and work by adsorption and desorption
What is autocatalysis?
When the product of a reaction acts as a catalyst for that reaction
What does the area under the curve resemble in the Boltzmann Distribution?
The total number of particles
What effect does increasing temperature have on the Boltzmann curve?
It stretches the curve horizontally, lowering the maximum point, but the total area remains the same
What is Le Chatelier’s Principle?
When a system is in a dynamic equilibrium and is subjected to an external change, the system will readjust itself to counteract the change
In a dynamic equilibrium, what effect will increasing the temperature have?
It will encourage the endothermic direction, to oppose the increase
In a dynamic equilibrium, what effect will increasing the pressure have?
It will encourage the reaction that produces fewer moles of gas, to oppose the increase
