Chemistry (Cambridge 0620 IGCSE) Flashcards
PANIC
Positive Anode Negative Is Cathode
What are Isotopes?
Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons.
State the relative charges and masses of protons, neutrons and electrons.
- Protons
Relative charge +1
Relative mass 1 - Neutrons
Relative charge 0 (neutral)
Relative mass 1 - Electrons
Relative charge -1
Relative mass very small (0.0005, or often just written as 0)
OILRIG
Oxidation is Loss, Reduction Is Gain (of electrons)
Explain the different states of matter
- Solids - have fixed shapes, fixed volume and the particles inside are tightly packed
- Liquids - have a fixed volume but they can take the shape of its container, particles inside can move around a bit.
- Gases - have no fixed volume, they take the shape of their container and particles inside can move around freely.
Explain in terms of structure of and bondings the properties of metals
- good electrical conductivity
- maleabillity and ductile
What are electrodes?
The parts (rods) of the electrolysis circuit dipped in the electrolyte (e.g carbon/graphite or platinum: inerts)
What is an electrolyte?
A liquid: a solution consists of partially dissociated ions
What elements are always present in any electrolyte solution?
H+ and OH- (dissociated from H₂O)
What are Cataions and Anions?
- Cations are positive ions (+), and are attracted to the Cathode (-)
- Anions are negative ions (-), and are attracted to the Anode (+)
CAP
Cations Are Positive
What is the Redox that happens at the electrodes?
- At the Cathode, Cations are Reduced.
- At the Anode, Anions are Oxidised
What are the rules that determine what will be produced at each electrode?
In a SOLUTION
- Rule 1: the LESS REACTIVE CATION is REDUCED at the cathode, while the more reactive stays in the solution.
- Rule 2: if there is a HALIDE ion (F-, Br-, Cl-, I-) they’re Always OXIDISED at the ANODE. (If it is anything other than a Halide, the element stays in the solution and oxygen bubbles off at the Anode).
In a MOLTEN SOLUTION
The electrolysis of a molten ionic compound always gives a metal at the CATHODE, and a non-metal at the ANODE
What four metals are LESS reactive than hydrogen?
(In order of reactivity from highest to lowest) Copper, Silver, Gold and Platinum.
Describe the two rods found in all electrolysis circuit.
- Cathodes are negative (-)
- Anodes are positive (+)
(Usually made from inert elements such as Carbon)
State the three steps when purifying metals (e.g copper).
(The Cathode is Pure copper while the Anode is impure copper)
1. The Copper in the impure anode is OXIDISED, and the ions enter the solution.
2. Insoluable impurities cannot be oxidised, so they stay solid and sink to the bottom.
3. The (copper) ions in the solution move to the Cathode where they are REDUCED and turned back into atoms, and are depositied.
How many atoms/particle/molecules are in one mole?
1 Mole = 6.02 x 10²³ (this huge number is also known as Avogrado’s constant).
What is Aᵣ?
Relative Atomic Mass (RAM) tells you what the mass of 1 MOLE of that specific element. (e.g Carbon’s Aᵣ is 12, stated above the ‘C’ in the periodic table).
How do you find 1 MOLE of something.
MOLE = ?÷?
1 MOLE = ‘GRAMS’ ÷ ‘RAMS’
or
1 MOLE = Mass (g) ÷ relative atomic mass (Aᵣ) / formula mass.
If carbon has an Aᵣ of 12, and there are 24g of carbon on a table how many moles are there? Answer: 12 ÷ 24 = 2 mol, so there are 2 moles of carbon on the table.
RAM
Relative Atomic Mass
Calculating concentrations
Concentration = Mass (g) or moles ÷ Volume (dm³)
(Concentration g/dm³ or mol/dm³. the “/” tells you its that mass over that volume).
Calculating dm³ from cm³
x cm³ ÷ 1000 = x dm³
