paper 2 Flashcards
Concentration = (of a solution)
moles (mol) / volume of solution (dm^3)
Number of Moles = (in a solution)
concentration (mol/dm^3) x volume (dm^3)
Volume = (in a solution)
Moles (mol) / Concentration (mol/dm^3)
Grams per dm^3 =
Mass of chemical (g) / volume of solvent (dm^3)
Avagrado’s Law =
One mole of gas occupies 24 dm^3
Convert the moles of any gas at RTP to a volume:
Volume (dm^3) = Moles of gas x 24
Calculating volumes in reactions with known masses:
1) Calculate the moles of the known substance.
2) Find the moles of gas using the balanced equation.
3) Convert the moles into a volume using vol = mol x 24
Define Electrolysis:
Breaking down of a substance using electricity
What is Oxidation and Reduction?
Oxidation is the loss of electrons
Reduction is the gain of electrons
What is a cation?
positive ions in the electrolyte
What is a cathode?
The negative electrode
What is the anode?
The positive electrode
How does electrolysis occur?
An electric current is passed through an electrolyte (molten or dissolved ionic compound), causing it to decompose.
Why can molten ionic compounds be electrolylsed?
The ions can move freely
What is an ionic half equation?
They show what is happening at each electrode, (splits the equation up so it is easier to understand).
What is attracted to the cathode?
The Positive (+ve) ions are attracted to the cathode (-ve)
What is attracted to the anode?
The Negative (-ve) ions are attracted to the anode (+ve).
What are the electrodes made from?
Inert material so they don’t take part in the reaction.
What is an electrochemical cell, and what components are in them?
A circuit made from an anode, cathode, electrolyte, power source and wires connecting the electrodes.
Which inert elements are usually used in the electrodes?
Graphite or Platinum
Why are aqueous solutions harder to electrolyse?
Aqueous solutions contain all the ions from the ionic compound as well as Hydrogen and Hydroxide ions from the water.
What is the charge on ions
Hydrogen and Hydroxide
Hydrogen = H+ Hydroxide = OH-
At the cathode in an Aqueous solution, what happens if Hydrogen & Metal Ions are present?
If hydrogen is more reactive than the Metal then Hydrogen gas is produced.
If the Metal ion is more reactive than Hydrogen then a solid pure metal layer is produced.
At the anode in an Aqueous solution, what happens is Hydroxide and Halide Ions are present?
Molecules of Chlorine, Bromine or Iodine will be formed.
How many electrons are present in the outer shell of group 1 elements.
1 outer shell electron
Why do atoms become more reactive as you move down the group? (in group 1)
The outer shell electron is further from the nucleus, meaning there is less attraction between them. The outer shell electron is more easily lost and they become more reactive.
How many atoms does a Halogen need to gain to form a stable outer shell?
Needs to gain an electron and form a 1 - atom.
Does reactivity decrease or increase for Halogens as they go down the group.
Reactivity decreases as the outer shell is further away from the nucleus so the attraction is weaker.
What are reaction profiles?
Diagrams that show the relative energies of the reactants and products in a reaction, and how energy changes in the course of a reaction.
In an reaction profile for an endothermic reaction, which has more energy, the products or reactants?
The products, as the energy is taken in during the reaction
In an reaction profile for an exothermic reaction, which has more energy, the products or reactants?
The reactants, as energy is given out during the reaction
