Topic C4- Predicting and Identifying Reactions and Products Flashcards
What are group 1 metals called?
Alkali metals.
What are the group 1 metals?
Lithium, Sodium, Potassium, Rubidium, Caesium and Francium.
Why do all group 1 elements have similar chemical properties?
They all have 1 outer electron.
What physical properties do all alkali metals have?
- Low melting points and boiling points (compared with other metals)
- Low density- lithium, sodium and potassium float on water.
- Very soft- they can be cut with a knife.
How can you test for the presence of group 1 metals?
Flame tests.
Why are group 1 metals very reactive?
- the group 1 metals readily lose their single outer electron to form a 1+ ion with a stable electronic structure.
- The more readily a metal loses its outer electron, the more reactive it is- so group 1 metals are very reactive.
- As the periods decrease in group 1, the alkali metals get more reactive.
- The outer electron is more easily lost because it is further from the nucleus (atomic radius is larger)
- so it is less strongly attracted to the nucleus and less energy is needed to remove it.
What happens when alkali metals are put in water?
- they produce hydrogen gas and hydroxide of the metal.
e. g. 2Na + 2H2O -> 2NaOH + H2
What are group 7 elements called?
Halogens.
Why do group 7 elements all have similar chemical properties?
They all have 7 electrons in their outer shell.
What is a diatomic molecule?
Diatomic molecules are molecules composed of only two atoms, of the same or different chemical elements.
What happens to halogens as you descend the periods?
- The melting points and boiling points of the halogens increase.
- They halogens become less reactive- it gets harder to attract the extra electron to fill the outer shell when it’s further away from the nucleus. (Atomic radius is larger.)
What does a reaction between halogens and alkali metals form?
They form salts- called metal halides.
What is a displacement reaction?
Where a more reactive element displaces a less reactive element from a compound.
How can you use displacement reactions to show reactivity trends?
1) Start by measuring out a small amount of halide salt solution in a test tube.
2) Add a few drops of a halogen solution. Shake tube gently.
3) If you see a colour change, then a reaction has happened- the halogen has displaced the halide ions from the salt.
4) Repeat the process using different combinations of halide salt and halogen.
What is the name given to Group 0 elements?
Noble Gases.
What are the elements in group 0?
Helium, Neon, Argon, Krypton, Xenon and Radon.
What are the properties of the noble gases?
1) All of the elements of group 0 are colourless gases at room temperature.
2) The noble gases are all monatomic- made up of single atoms.
3) They’re inert- they don’t react with much at all.
4) They have a full outer shell, so they don’t easily gain or lose electrons.
5) They are non-flammable.
What are the trends in group 0 elements as you descend down the periods?
The boiling points, melting point, and density all increase as you go down the periods.
What are the typical metallic properties of transition metals?
They are:
- hard
- shiny
- strong
- conduct heat
- conduct electricity
- high melting and boiling points (except mercury)
- high densities.
- have more than one ion (e.g. Fe2+, Fe3+)
- Their compounds are very colourful.
- relatively unreactive.
Which transition metal is used as a catalyst in the Haber Process?
Iron.
Which transition metal is used as a catalyst in the Contact Process?
Vanadium Pentoxide.
How do metals reacting with acids tell you about their reactivity?
1) The easier it is for a metal to lose its outer electrons and form a positive ion, the more reactive it will be.
2) The more reactive the metal, the faster the reaction will go.
3) Very reactive metals (Mg) will fizz vigorously, less reactive metals (Zn) will bubble a bit, and unreactive metals (Cu) will not react with dilute acids at all.
4) You can show that hydrogen is forming using the burning splint test. The louder the squeaky pop, the mor ehydrogen has been made in the time period and the more reactive the metal is.
5) Speed of reaction is indicated by the rate at which the bubbles of hydrogen are given off- the faster the bubbles form, the faster the reaction and the more reactive the metal. (*gas syringe to measure volume of gas given off at regular intervals.)
Complete the formula:
metal + water –>…:
metal + water –> metal hydroxide + hydrogen.
Name the metals in the reactivity series, from the most reactive to the least reactive:
Potassium Sodium Calcium Magnesium Aluminium Zinc Iron Copper Silver
What happens if you put a more reactive metal into a solution of a less reactive metal salt?
The more reactive metal will replace the less reactive metal in the salt.
What happens if you put a less reactive metal into a solution of a more reactive metal salt?
Nothing will happen- the more reactive metal is already in the salt.
How can you test for carbon dioxide?
Use limewater:
- bubble co2 through limewater
- if gas is co2, then the limewater will turn cloudy
How can you test for hydrogen?
- Hydrogen makes a squeaky pop with a lighted splint.
- The noise comes from the hydrogen burning with the oxygen in the air to form water.
How can you test for oxygen?
Use a glowing splint- if oxygen is present than it will relight a glowing splint.
How can you test for chlorine?
Using a damp blue litmus paper:
- hold piece of damp blue litmus paper over gas.
- if gas is chlorine, it will bleach the litmus paper, turning it white.
- it may also turn red at first- that is because a solution of chlorine is acidic.
How can you test for halide ions?
Using Silver Nitrate Solution:
- To test for Cl- ions, Br- ions or I- ions, add some dilute nitric acid
- followed by a dew drops of silver nitrate.
The results should show:
- chlorine gives a white precipitate of silver chloride.
- bromide gives a cream precipitate of silver bromide.
- iodide gives a yellow precipitate of silver iodide.
How can you test for carbonates?
Using Hydrochloric Acid:
- to test for carbonate ions, add some barium chloride solution.
- if there are carbonate ions present, this will produce a white precipitate of barium carbonate.
- then you add some dilute hydrochloric acid.
- if there are carbonate ions present, the mixture will fizz (carbonate reacts with acid to produce carbon dioxide).
- if you collect the gas and pas it through limewater, the limewater should turn cloudy.
- once all the barium carbonate has reacted, there will be a colourless solution containing Ba2+ ions.
How can you test for sulfate ions?
Using Barium Chloride Solution:
- add some barium chloride solution.
- if there are sulfate ions in the solution, a white precipitate will form.
- then add dilute hydrochloric acid
- barium sulfate will not react with the dilute hydrochloric acid, so white precipitate will not dissolve (this is how you know you have sulfate ions and not carbonate ions.)
How can you identify metal ions in a compound?
Using flame tests:
Compounds will produce a characteristic colour when heated in the flame.
To carry out a flame test, clean a nichrome wire loop by dipping it in hydrochloric acid and rinse it with deionised water.
Dip the wire loop into sample of metal compound and put the loop in the clear blue part of the Bunsen Burner.
The colour for each metal: Lithium- crimson red flame Sodium- yellow flame Potassium- lilac flame Calcium- brick red flame Copper- blue-green flame.
What are the advantages for instrumental analysis methods?
- they are very sensitive: detect even the smallest amounts of a substance.
- they are fast
- they are very accurate- don’t involve human error, as manual analysis does.
What are some examples of instrumental analysis?
- Infrared Spectroscopy
- Ultraviolet Spectroscopy
- Gas Chromatography
- Mass Spectrometry
