C4 - Predicting and Identifying Reactions / Products Flashcards
What is the other name for Group 1 elements?
Alkali metals - they react with water to form an alkali (a metal hydroxide)
List the group 1 metal:
Lithium, Sodium, potassium, rubidium, caesium, francium
What is the physical properties of group 1 metals?
- They are soft - can be cut by knife
- They have low density - lithium, sodium and potassium can float on water
- Low melting and boiling points
Group 1 metals and reactivity:
The reactivity depends on how easily it is to lose an electron.
Reactivity increases as you go down the periodic table:
1) Outermost electron furthest from the positive nucleas. The force of attraction is weaker. Electron easily lost.
2) Electron shielding - there are more electrons in the inner shells as you go down to repel outermost electron.
What happens when alkali metal reacts with cold water:
-They react vigorously
-The reaction produces a hydroxide of the metal and hydrogen gas.
EG:
Sodium + water -> sodium hydroxide + hydrogen gas
-The reactivity increases as you go down periodic table:
Lithium: moves around surface and fizzes furiously
Sodium and potassium: do same but melt from heat of reaction. Potassium - lilac flame can be seen - can ignite the hydrogen gas
Rubidium and Caesium: explode when wet
What happens when alkali metal react with dilute acid?
They produce a salt and hydrogen gas
EG:
Sodium + hydrochloric acid -> sodium chloride + hydrogen
What is the other name for group 7 elements?
Halogen
List the Group 7 elements:
Florine, Chlorine, Bromine, Iodine, Astatine
What do Group 7 metals exist as?
They are diatomic so F2, Cl2, Br2, I2 , At2
How does Chlorine, Bromine, Iodine look like at room temperature?
- > Chlorine: poisonous, green gas
- > Bromine: poisonous, Red-brown liquid giving off orange vapour
- > Iodine: dark grey crystalline solid giving off purple vapour when heated
Halogens and reactivity:
Reactivity depends on how easily it is to gain an electron.
Therefore reactivity decreases as you go down the periodic:
As you go down it gets harder to attract electron as shell is further away from positive nucleus.
What happens when halogens react with alkali metals?
They form salts called ‘metal halides’
EG
Sodium + Chlorine -> Sodium Chloride
What are halogen displacement reaction?
When a more reactive halogen ‘pushes out’ a less reactive halogen in a reaction.
EG
Chlorine + Potassium Bromide -> Potassium chloride + Bromine
1) The Chlorine will displace the Bromine
2) Chlorine is reduced to ions, so salt solution becomes Potassium Chloride.
3) The Bromide ions are oxidised into Bromine, turning solution orange
How do you know in chemical test if halogen has been displaced?
You will see a colour change
What happens when you add Chlorine water (colourless) to:
- Potassium Chloride solution
- Potassium Bromide solution
- Potassium Iodide solution
Potassium Chloride (KCl) -colourless : NO REACTION
Potassium Bromide (KBr) - Colourless: Orange solution (Br2) formed as chlorine displaces Bromine. Bromine ions turn solution orange.
Potassium Iodine (KI) - colourless: Brown solution (I2) formed as chlorine more reactive. The iodine ions make solution Brown.
What happens when you add Bromine water (Orange) to:
- Potassium Chloride solution
- Potassium Bromide solution
- Potassium Iodide solution
Potassium Chloride (KCl) -colourless : NO REACTION
Potassium Bromide (KBr) - Colourless: NO REACTION
Potassium Iodine (KI) - colourless: Brown solution formed (I2) as bromine is more reactive than Iodine. The displaced iodine ions turn solution brown.
What happens when you add Iodide water (Brown) to:
- Potassium Chloride solution
- Potassium Bromide solution
- Potassium Iodide solution
Potassium Chloride (KCl) -colourless : NO REACTION
Potassium Bromide (KBr) - Colourless: NO REACTION
Potassium Iodine (KI) - colourless: NO REACTION
What is the other name for Group 0 elements?
Noble Gases
list the Noble gases:
Helium, Neon, Argon, Krypton, Xenon, Radon
What are some properties of noble gases?
- They are colourless
- They are inert (unreactive) and monoatomic as they have full outer most shells -> hard to gain or lose electrons
- because they are inert they are non-flammable
Noble gases and melting / boiling points and density:
As you go down:
Melting / boiling point: increases
Density: increases
Where are transition metals on the periodic table?
They are in the middle (between group 2 and 3)
What are the typical metallic properties of transition metals?
1) Typical metallic properties like hard, strong, and shiny
2) Conduct electricity and heat
3) High melting/boiling points (except mercury)
4) High densities
What are more general properties of transition metals?
1) They make good catalyst
- Iron catalyst used in Haber process to make ammonia
- Vanadium pentoxide catalyst for making sulphuric acid in Contact Process
2)Often have more than one ion (Fe2+, Fe3+, Cu+, Cu2+)
3) Their compounds are colourful
Eg -> Compounds containing Fe2+ are usually light green
Fe3+ are usually orange/brown
Cu2+ are usually blue
4) They are often relatively unreactive compared to group 1 and 2 metals
Experiment to test the reactivity of metals with acid:
- Place various metals in dilute hydrochloric acid and the faster reaction goes, the more reactive it is (use a stopwatch)
- When metals react with acid they produce hydrogen gas -> the more hydrogen produced more reactive.
Expected results from the metal reactivity test with acid:
Most reactive to least:
1) Magnesium - fizz most, burning splint goes of with loud squeaky pop
2) Aluminium
3) Zinc
4) Iron
5) Copper - no fizzing, burning splint doesn’t go out at all
As you go up reactivity series the more reactive metal, the louder the squeaky pop.
What is the word equation for metals reacting with water?
What is the word equation for a less reactive metal?
Metal + water -> Metal hydroxide + hydrogen
Less reactive metal doesn’t react with water but it does with steam:
Less reactive metal + steam -> metal oxide + hydrogen
The reactivity series:
Please Potassium Send Sodium Lions Lithium Cats Calcium Monkeys Magnesium And Aluminium Zebras Zinc Into Iron Lovely Lead Hot Hydrogen Countries Copper Signed Silver General Gold Penguin Platinum
What are metal displacement reactions?
-A more reactive metal will displace a less reactive metal in displacement reaction
EG Copper sulphate + iron -> Iron sulphate + copper
-If a less reactive metal is introduced in reaction, nothing will occur
How to test for Carbon dioxide gas?
It turns limewater cloudy when it is run through it
How to test for Hydrogen gas?
It makes burning splint go off with a squeaky pop
How to test for Oxygen?
It reignites a glowing splint
How to test for Chlorine gas?
It bleaches a damp litmus paper
How to test for halide ions?
- Add nitric acid to rid of all the carbonate ions
- Add silver nitrate solution
1) Chlorine = white precipitate of silver chloride
2) Bromine = cream precipitate of silver bromide
3) Iodine = yellow precipitate of silver iodide
How do you test for carbonates?
- Add barium chloride solution, if carbonate ions present white precipitate is formed (this is either carbonates or sulphate ions).
- Add dilute hydrochloric acid
If precipitate reacts, carbonate are present ,carbon dioxide is produced
-To see if it is carbon dioxide run it through limewater
How do you test for sulphate ions?
-Add barium chloride solution
If sulphate ions present a white precipitate is form
-> Then add Hydrochloric acid, if the precipitate doesn’t react it is Sulphate ions instead of Carbonate ions
Flame test method:
1) Use moistened flame test wire (with dilute hydrochloric acid)
2) Dip flame test wire in solid sample
3) Put flame test wire over flame and record results
Expected results of test for Cations in flame test?
- > Lithium (Li+) = Crimson red flame
- > Sodium (Na+) = Yellow flame
- > Potassium (K+) = Lilac flame
- > Calcium (Ca2+) = Red flame
- > Copper (Cu2+) = Blue/Green flame
How to test for metals using sodium hydroxide?
It forms coloured precipitates when you add sodium hydroxide to the metal.
- Copper (Cu2+) = Blue precipitate
- Iron (Fe2+) = Green precipitate
- Iron (Fe3+) = Brown precipitate
- Calcium(Ca2+) = white precipitate
- Zinc (Zn2+) =White precipitate, excess, dissolves when excess sodium hydroxide added
What is the difference between Chemical test and Instrumental methods?
Chemical test - manual ways of analysing substances
Instrumental methods - Using machines to analyse substances
Advantages and disadvantages of Chemical test?
Advantages:
- Quick and cheap
- Little specialised training need
Disadvantages:
- limited to gases and ions
- Not very sensitive
- Not quantitative (doesn’t tell you how much in each sample)
- Some reagents harmful
Advantages and disadvantages of Instrumental methods?
Advantages:
- Accurate, quick and sensitive
- Quantitative
- Can be carried out continuously
Disadvantage:
-Expensive equipment
-Specialised training needed
Results need to be compared to other substances
What is mass spectrometry used for?
- Identifying unknown substances
- Find molecular mass
- Determine the abundance (percentage) of each isotope
- Gather information about structure and chemical properties of molecules
How do you identify the molecular mass of substance from mass spectrogram?
The last peak of the graph is the molecular mass.
How do you identify a substance from chromatogram?
The retention: the time taken for the substance to pass through equipment.
It is the measurement from the peaks to the y axis.
General equation for a reaction of an alkali metal and water:
Alkali metal + water - > metal hydroxide + hydrogen
5 acid equation:
1) Acid + Metal oxide-> Salt + water
2) Acid + Metal hydroxide -> Salt + water
3) Acid + Alkali -> Salt + Water
4) Acid + Metal -> Salt + Hydrogen
5) Acid + Metal carbonate -> Salt + Water + Carbon dioxide
