Chemistry of the Elements Flashcards
Describe group 0
noble gases are inert, colourless gases
have a full outer shell so no need to react
Describe what happens when group 1 elements with water
react vigorously, producing a metal hydroxide solution
the solution is alkaline, and also produces hydrogen
Group 1 + water —– Group 1 hydroxide + hydrogen
Describe what happens when Lithium reacts with water
fizzes slightly for 30s
Describe what happens when Sodium reacts with water
fizzes for 20s may ignite
Describe what happens when Potassium reacts with water
lilac flame for 5s sometimes explodes
Why do atoms in group 1 react easier as you go down the group ?
only 1 electron in their outer shell - want to react
going down, outer electron gets further from nucleus
attraction from outer electron and nucleus decrease
Describe halogens as you go up / down the group
Group 7
as you go down: darker colour and higher boiling point
as you go up: more reactive as missing electron is nearer to nucleus so electrostatic force is greater
Chlorine :
colour -
physical state (RT) -
boiling point -
Chlorine :
colour : green
physical state (RT) : gas
boiling point : -34
Bromine :
colour -
physical state (RT) -
boiling point -
Bromine :
colour - red / brown
physical state (RT) - liquid
boiling point - 59
Iodine :
colour -
physical state (RT) -
boiling point -
Iodine :
colour - dark grey
physical state (RT) - solid
boiling point - 185
Describe dissociation
Hydrogen Chloride (HCl) is a gas and dissociates in water, splitting into H+ and Cl- ions, this is dissociation
the solution formed is hydrochloric acid (acid)
testing the solution with litmus paper will make it red
Describe dissociation in methylbenzene
HCl does not dissociate in methylbenzene
no H+ ions means it is not acidic
testing the solution with litmus paper will stay blue
what is a displacement reaction ?
more reactive element displaces (pushes out) a less reactive element from a compound
involves transfer of electrons
Describe halogen displacement reactions
Halogens take part in displacement reactions
higher up in group 7 - more reactive
this will sometimes change the colour of solution
Give an example of a halogen displacement reaction
chlorine is more reactive than iodine
chlorine water + potassium iodide solution
chlorine react with potassium to form potassium chloride, iodine left over changing solution brown
Give an experiment for halogen displacement
add a few drops of halogen solution to salt solution
look for colour change
what is the name for loss of electrons ?
oxidation
what is the name for gain of electrons ?
reduction
what is an oxidising agent ?
receives electrons (gain) and gets reduced
what is a reducing agent ?
gives electrons (loss) and gets oxidises
what is a redox reaction ?
reaction with both oxidation and reduction recurring
acid + metal —
salt + hydrogen
Metal + Water —
Metal Hydroxide + Hydrogen
(less reactive metal + steam —
Metal oxide + Hydrogen)
Describe some metals reacting with water
sodium, lithium and potassium react vigorously
magnesium, zinc and iron won’t react with water, but will react with steam
Copper won’t react with water or steam
state the reactivity series
Potassium, Sodium, Lithium, Calcium, Magnesium, Aluminium, Zinc, Iron, Copper, Silver, Gold
how does rust occur ?
what type of reaction is this?
iron rusts when it is in contact with oxygen and water
oxidation reaction as iron gains oxygen (iron oxide)
state the equation for rust
iron + oxygen + water — hydrated iron(III) oxide
what are the 2 main ways of preventing rust
barrier method
sacrificial method
describe the barrier method for rust
paint/coat with plastic - ideal for structures
oil/grease - used on moving parts like bike chains
describe the sacrificial method for rust
place a more reactive metal with iron so water/oxygen get sacrificial metal instead
zinc is often used, spraying a coat of zinc is called galvanising, or big blocks can be bolted to the iron
What are the gas percentages in the air ?
78% nitrogen
21% oxygen
1% argon
0.04% carbon dioxide
what happens when an element burns in the air ?
it reacts with the oxygen to form an oxide
these oxides can either have acid or base character
Describe magnesium burnt in air
what is formed?
burns bright white flame
white powder formed (magnesium oxide)
magnesium oxide slightly alkaline dissolved in water
Describe Carbon burnt in air
what is formed?
will burn in air if very strongly heated
orange/yellow flame and produces carbon dioxide
carbon dioxide is slightly acidic dissolved in water
Describe sulfur burnt in air
what is formed?
pale blue flame
produces sulfur dioxide
sulfur dioxide is acidic when dissolved in water
when do you use upward delivery ?
collect gasses light that air
when do you use downward delivery ?
collect gasses heavier than air
Describe the use for carbon dioxide in fizzy drinks
CO² is slightly soluble in water and dissolves into drink under pressure,as CO² is acidic (slightly) it creates a carbonic acid
bubbles in fizzy drinks are CO² escaping
Describe the use for carbon dioxide in fire extinguishers
CO² is denser than air so sinks onto flames and stops oxygen getting to it (suffocates)
CO² fire extinguishers used when water isn’t safe (electrical fires)
Why is Carbon dioxide a problem in the atmosphere?
gases in atmosphere like CO² and methane act as an insulating layer, absorbing the heat radiated back from earth, and radiates it back
more CO² is being released than removed
How is human activity affecting CO² concentration in the atmosphere ?
deforestation - fewer trees means less CO² removed via photosynthesis
burning fossil fuels - carbon in fossil fuels released as CO²
How is carbon dioxide linked to global warming ?
correlation between temperature of earth and concentration of CO²
global warming is a type of climate change
causes flooding due to ice caps melting
Describe the sodium flame test
yellow-orange flame
Describe the potassium flame test
lilac flame
Describe the calcium flame test
brick-red flame
How do you test for a cation?
clean a platinum wire loop in dilute HCl and hold in flame, once it burns without any colour then dip in sample and put in flame, observing colour
are (most) metal hydroxides soluble or insoluble?
metal hydroxides are insoluble
Copper (II) + Sodium hydroxide (NaOH)
Colour of precipitate:
Copper (II) + Sodium hydroxide (NaOH)
Colour of precipitate: blue
Iron (II) + Sodium hydroxide (NaOH)
Colour of precipitate:
Copper (III) + Sodium hydroxide (NaOH)
Colour of precipitate: green
Iron (III) + Sodium hydroxide (NaOH)
Colour of precipitate:
Iron (III) + Sodium hydroxide (NaOH)
Colour of precipitate: reddish brown
Ammonium + Sodium hydroxide (NaOH)
produces ammonia gas, gives off pungent smell
ammonium is colourless
state the test for ammonia gas
use damp piece of red litmus paper
if turns blue, ammonia is present
ammonia gives off pungent smell
How do you test if substance contains ammonium ions ?
add some sodium hydroxide (NaOH) to substance
If ammonia gas given off, ammonium ions present
(damp red litmus paper turns blue)
what is anion ?
a negatively charged ion
state the test for carbonates
add dilute HCl to test sample
If carbonates present, CO² given off
state the test for sulfates
sulfate ions produce a white precipitate
add HCl followed by barium chloride, white precipitate of barium sulfate means original compound was a sulfate (HCl added to rid any traces of carbonate or sulfite ions as these would produce a precipitate)
state the test for Halides (Cl, Br, I)
add dilute nitric acid, followed by silver nitrate solution
(acid used to rid carbonate or sulfite ions)
observe colour
Describe the halide test for Chlorine + silver nitrate
gives white precipitate of silver chloride
Describe the halide test for Bromine + silver nitrate
gives a cream precipitate of silver bromide
Describe the halide test for Iodine + silver nitrate
gives a yellow precipitate of silver iodide
State the test for chlorine
bleaches (turns white) damp litmus paper
State the test for oxygen
place glowing splint by test tube, splint will relight if oxygen present
State the test for CO²
CO² turns lime water cloudy - bubble gas through a test tube of time water
State the test for hydrogen
hydrogen makes a squeaky pop with a lit splint
noise is hydrogen burning with oxygen in air to form H²O
State the test for water
Anhydrous Copper (II) sulfate is white Hydrated Copper(II) sulfate is blue add anhydrous copper (II) sulfate to sample, will turn blue if water is present
State the test for pure water
pure water will always : boil at 100°C
freeze at 0°C
Flame test for Lithium
Crimson red flame
Calorimetry example (not combustion)
Add acid to polystyrene cup, record temp
add base to measuring cylinder, record temp
add base to acid and stir
record temp every 30s and find highest temp
(surround cup with cotton wool and put lid)
Calorimetry example (combustion)
50g of water in metal (copper) can and record temp
weigh spirit burner and lid
light and hold under can until 50 degrees
measure final temp (water)
weigh spirit burner and lid
(use draught excluder)
