UCAS Mock Flashcards
What is the volume of one mole of a gas?
24dm-3 or 24000cm-1
Calculate gas volume using moles
Volume = moles x 24
Avogadros constant
6.02 x 10^23
Ideal gas equation
pV = nRT
Units for ideal gas equation
p = Pa
V = m^3
T = Kelvin
Calculating mean titre things to remember
- only use concordant results (within 0.1cm^3 of each other)
- don’t include the rough titre
% yield
Actual / theoretical
Oxidation number of group1
+1
Oxidation number of group 2
+2
Oxidation number of group 7 ions
-1 if alone but can be variable
Oxidation number of oxygen
-2 unless in peroxide
Oxidation number of hydrogen
+1 unless in a metal hydride
Oxidation number of fluorine
ALWAYS -1
Energy change
q = mcΔT (in joules)
Test for carbonate ions
Add nitric acid
- if positive test, there’s effervescence as CO2 is produced
- test gas with lime water to confirm
Test for sulfate ions
Add aqueous barium chloride
- positive test: white precipitate formed (BaSO4)
Test for halides
Add aqueous silver nitrate
- positive test: precipitate formed
How to identify the precipitate formed in halide test
White - silver chloride
Cream - silver bromide
Yellow - silver iodide
How to confirm halide tests if colours are difficult to determine
Dilute NH3: AgCl is soluble, AgBr and AgI are insoluble
Conc NH3: AgBr is soluble, AgI is insoluble
Test for ammonium ions
Heat with NaOH(aq)
- positive test, OH- reacts with NH4+ forming NH3(g) which you test with damp indicator paper (alkaline)
Group 2 + oxygen
Group 2 metal oxide
Group 2 + water
Group 2 metal hydroxide + hydrogen
Group 2 + dilute acid
Group 2 metal salt + hydrogen gas
Group 2 oxide + water
(Group 2 ion)^2+ + 2OH-
How are group 2 reducing agents
Donate electrons, other species are reduced
Trend in group 2 reactivity
Increases down group
Atomic radius and electron shielding increase (more shells)
Less attraction between outer electron and nucleus
Solubility and PH trend in group 2 hydroxides
Increase down group
Solubility and PH trend in group 2 sulfates
Decreases down group
Uses of calcium hydroxide
Lime - neutralise acidic fam soil for crops
Medical uses of group 2
- indigestion tablets neutralise excess stomach acid (Mg(OH)2 = milk of magnesia and CaCO3)
- barium meal for x-rays
Why are group 7 known as oxidising agents
Gain electrons causing other species to be reduced
Colour of halogens in water
Cl - pale green
Br - orange
I - brown
Colour of halogens in cyclohexane
Cl - pale green
Br - orange
I - purple/ violet
Displacement of halogens
Reactivity decreases down group
- chlorine displaces bromine + iodine
- bromine displaces iodine
Water purification using chlorine
Cl2 + H2O —> HClO + HCl
- HClO acts as a weak bleach that kills bacteria
Water purification using chlorine
Cl2 + H2O —> HClO + HCl
- HClO acts as a weak bleach that kills bacteria
Benefits and risks of using chlorine in the water purification
Benefits:
– Cleans water makes it safe to drink
Risks:
– chlorine is a toxic gas, can react with hydrocarbons to form chlorinated hydrocarbons, which are suspected of causing cancer
Benefits and risks of using chlorine in the water purification
Benefits:
– Cleans water makes it safe to drink
Risks:
– chlorine is a toxic gas, can react with hydrocarbons to form chlorinated hydrocarbons, which are suspected of causing cancer
Dissociation of a strong acid
irreversible reaction (One way reaction)
Dissociation of a weak acid
Reversible reaction
Acid + alkali
Salt + water
Metal oxide + acid
Salt + water
Metal hydroxide + acid
Salt + water
Metal carbonate + acid
Salt + water + carbon dioxide
Neutralisation ionic equation
OH-(aq) + H+(aq) —-> H2O(l)
