Chemistry IGCSE Flashcards
To help revise for the Edexcel Certificate in Chemistry
moles of substance?
moles = mass / Mr
moles of a gas (standard temperature and pressure)?
moles = Volume / 24 dm^3
moles of an aqueous solution?
moles = Volume x concentration
What two substances could be produced at the anode of the electrolysis of an aqueous substance?
Oxygen or a non-metal
Name three experiments to find oxygen concentration in air
Copper; Iron filings; Phosphorus
Sulphur + oxygen
sulphur dioxide (colourless) and lilac flame
Describe lab preparation of carbon dioxide
Put hydrochloric acid and calcium carbonate in a test tube with a bung with a tube which goes into limewater; if the gas produced (bubbling) is CO2, the limewater will turn cloudy, forming CaCO3 precipitates
What is observed when heating CuCO3?
CuCO3 decomposes into BLACK CuO (copper (II) oxide) and CO2 gas
What is observed when ZnCO3 is heated?
Colour change; white to yellow; ZnCO3 -> ZnO + CO2
Describe manufacture of ethanol by hydration of ethene
Ethene passed over steam with Phosphoric acid catalyst. 300°C, 60-70 atm.
Describe dehydration of ethanol to produce ethene
Pass ethanol over hot aluminium oxide catalyst
Phenolphtalein in acid
colourless
Methyl orange in alkali
yellow
Methyl orange in acid
red/orange
Methyl orange in neutral
yellow
Phenolphtalein in alkali
pink
Phenolphtalein in neutral
colourless
Litmus in Acid
red
Litmus in alkali
blue
Litmus in neutral
purple
Which salts are soluble?
Nitrates, Sodium/Potassium/Ammonium salts
Which chlorides are insoluble?
Silver chloride, Lead chloride
Which sulfates are insoluble?
Barium sulfate, calcium sulfate, lead sulfate
Are carbonates soluble or insoluble?
Most are insoluble (e.g. Calcium carbonate)
How do you make a soluble salt?
dilute acid + base; dilute acid + metal carbonate; dilute acid + metal
How do you make insoluble salts?
Precipitations
Is breaking bonds exo/endothermic?
ENDOTHERMIC
Is making bonds exo/endothermic?
EXOTHERMIC
Conditions for Haber process?
450°C, 200 atm, Iron catalyst
Conditions for contact process?
450°C, 2 atm, Vanadium oxide catalyst
Give three uses of sulfuric acid
fertilisers, paint, detergents
Give four uses of NaOH (sodium hydroxide)
soap, bleach, detergent, paper
How can you obtain NaOH and Chlorine?
Electrolysis of brine
Describe Addition Polymerisation
An alkene monomer is bonded with other monomers to form a polymer. However, the alkene becomes an alkane.
Describe Condensation Polymerisation
The monomers retain their bonds, but small molecules are lost; normally water, but sometimes NH3 or HCl
Is Calcium Chloride (CaCl2) soluble or insoluble?
SOLUBLE
Why do atoms in the same group of the periodic table have similar chemical properties?
Because they have the same number of valence electrons
Give another name for the elements in group 1
the Alkali Metals
How does Lithium react in water?
It moves on the surface of the water, it fizzes, melts and disappears
How does Sodium react in water?
It moves on the surface of the water, it fizzes, melts into a shiny ball and then disappears
How does Potassium react in water?
It moves on the surface of the water, it fizzes, melts into a shiny ball, produces a lilac flame, and eventually disappears.
What happens to the reactivity of group 1 metals as you go down the periodic table?
They become more reactive.
Why do group 1 metals become more reactive as you go down the periodic table?
Because the valence electron gets shielded by more shells further down the group, which decreases the electrostatic attraction between the valence electron and the nucleus, so it becomes easier for a metal further down to lose its valence electron and hence react.
Name the halogens
Fluorine, Chlorine, Bromine, Iodine, Astatine
What state and colour is chlorine at room temperature and pressure (rtp)?
Greenish gas
What state and colour is bromine at rtp?
Brown/orange liquid
What state and colour is iodine at rtp?
Black solid
Explain the reactivity of the halogens
The reactivity decreases as you go down the periodic table because there is only one valence electron missing to make a full outer shell, and the further down the periodic table you go, the lesser the electrostatic attraction between the valence electrons and the nucleus, so much more energy would be needed to react.
Why don’t HCl and methylbenzene form an acidic solution?
the H+ ions in HCl don’t ionise methylbenzene.
What does the Brønsted-Lowry theory of acids and bases state?
That acids contain H+ ions, and hence are proton donors, and bases contain OH- ions, and hence are proton acceptors
How do you determine atmospheric oxygen concentration using copper?
Attach two gas syringes to a silica tube (one on either side). Make sure that there are 100 cm^3 of air in the syringes. Place copper in the silica tube, and heat from below using a Bunsen burner. Pass the gas from one syringe to the other over the burning copper until the copper turns black (and becomes copper (II) oxide). Measure volume of gas syringes. It should be ~79cm^3, so 21% of gas was O2.
How do you determine the atmospheric oxygen concentration using iron?
Put iron filings at bottom of a burette and place upside down in a trough of water. Measure starting volume of water. Leave for a week. Measure final volume of water. Difference should be ~21%
What is formed when metal carbonates are heated (thermally decomposed)?
Carbon dioxide
What do metals above Hydrogen in the reactivity series form when reacted with HCl?
Metal chloride + Hydrogen
Metal + sulfuric acid?
metal + sulfuric acid –> metal sulfate + hydrogen
List the elements of the reactivity series in decreasing reactivity
Potassium; Sodium; Lithium; Calcium; Magnesium; Aluminium; Zinc; Iron; Tin; Lead; Hydrogen; Copper; Silver; Gold; Platinum
Useful mnemonic to remember reactivity series
Private Second-Class MACZITL He Can make Some Gun Powder
