C4 Flashcards
How are group 1, alkali metals similar in their electron configuration?
They allhave a single outer electron.
Why do alkali metals have similar chemical properties?
They all have a single outer electron.
What similar phyiscal properties do alkali metals have?
- low melting points compared to other metals
- low density
- very soft, can be cut with a knife
- form ionic bonds
Explain the trends of physical properties and rectivity in alkali metals?
-as you go down, melting pints go down
-as you go down, density increases
as you go down, rectivity increases
Why are alkali metals stored in oil?
They react vigourously with o2 in the air, so they are kept in oil.
What’s the alkali metal and water reaction?
metal is X
2X + 2H20 -> 2XOH + H2
eg) 2Na + 2H20 -> 2NaOH + H2
Why do the alkali metals get more reacive as you go down the group?
They become more reactive as you go down the group because they lose the outer electron more easily. The outer electron is lost easirly as the atom radius increases, so electron is further away from nucleus,so less attraction to nucles, lessenergy to remov it.
Why do halogens have similar chemical properties?
This is because they have 7 outer electrons..
What kind of molecules do halogens exist as?
They exist as diatomic molecules sharing a pair of electrons.
What kind of intermolecular forces do halogen molecules have?
They have weak intermolecular forces.
Explain the trend in physical properties as you go down group 7?
As you go down the group, melting point, boiling point and density increase.
What colour and states are halogens at room temperature?
At room temp:
- F2 is a pale yellow gas
- Cl2 is a green gas
- Br2 is a orange brown
- I2 is a grey, black crystaline that sublimes into purple vapour
How do halogens react with alkali metals?
They react vigourously with alkali metals to form a metal halide, salt
Explain the trend in halogen’s reactivity??
- Halogens get less reactive as you go down the group
- Halogens only need 1 outer electronfor stable electron structure.
The easier it is for an atom to attract and electron, the more reactive it will be. As you go down group 7, it gets harder to attract extra electron if it is furhter away from nucleus, the atom radius is largeer.
What is a halide?
A compound that has a halogen and another element
What is a halogen displacement reaction?
Halogens can react with halides in solutions. A halogen displacemnt reaction is when a halogen displaces the halide solution.
How does a halogen displacement reaction work?
A more reactive halogen displaces the less reactive halogen from a compound
What happens when you add chlorine water to potassium bromide solution?
Clorine is more reactive than bromine, so it displaces bromine from salt solution. Chorine reduced to chloride ions, so salt becomes potassium chloride. Bromide ions oxidised to bromine , turning solution orange
What colour are noble gases?
They are colourless
Why are noble gases inert?
Because they have a full outer shell, they on’t have a tendency to lose, gain or share lectrons to make molecules
Why do noble gases have low boiling points?
As they’re monatomic, their weak forces of attraction are easily overcome, so low heat is needed.
What is the trend in physical properties of group 8?
As you go down, boiling point, density, melting point all increase.
Why do noble gases have low density?
As theyre in gas state, particles are so far apart there is little mass in given volume.
Where are transition metals located?
Between group 2 and 3 of the periodic table.
What are the physical properties of transition metals?
- shiny when cut
- good conductors
- malleable
- strong
- high density
What’s the difference between transition metals and alkali metals in terms of reactivity?
Alkali metlas are much more reactive, if transition metals react, its very slow.
What is the difference between ionic compounds with alkali metlas and transition metals?
Alkali metlas produce white/colourless ionic compounds
trnasition metals produce coloured ionic compunds
What are transition metlas used for in industry?
They make good catalysts, iron usedto make ammonia in harber process
Vanadium pentoxide used to make sulfuric acid in contact process
used in car catalytic converters converting harmful gases to safe one
How do you test for CO2?
- Bubble gas through limewater
- If CO2 present it turns cloudy
Why does limewater turn cloudy when CO2 is bubbled through it?
- Lime water is calcium hydroxide
- Calcium hydroxide reacts with carbon dioxide to form water and white calcium carbonate precipitate
What is chemcial reaction for limewater and carbon dioxide?
CO2+Ca(OH)2->CaCO3+H2O
How do you test for hydrogen?
- Place lit splint near mouth of container
- If H2 present squeaky pop occurs
- Sound is H2 burning with 02 in air forming H2O
How do you test for O2?
-Place glowing splint near mouth of container if it relights O2 is present
How do you test for Cl2?
- Hold damp piece of blue litmus over mouth of container
- If gas is chlorine it will bleach it white
- It turns red for a second as Cl2 reacts with H20 on litmus making HCl, which has low ph, turning red
Why does the flame test work?
- When metal ions heated, energy transferred to electrons, making them move to higher shells
- When they move back to normal shell, energy is transferred to suroundings as radiation, can be seen in light
What colour flame do lithium and sodium produce?
Lithium-Red
Sodium-Yellow
What colour flame do potassium, calcium and copper produce?
Potassium- Lilac
Calcium- Orange-red
Copper-Green-Blue
Why can flame test not be used to identify metals of an sample with more than 1 metal ion?
You’ll get a mixture of colours
How do you carry out a flame test?
- First clean a nichrome wire by dipping it in hcl and rinsing with distilled water
- Once clean, therell be no colour change when held on a flame
- Dip in metal compound sample and put loop in clear part of blue flame
Why can sodium hydroxide precipitate test not be used for alkali metals?
-Alkali metals are soluble in water so they don’t for a precipitate
Why is sodium hydroxide used in experiments and not other metal hyrdoxides?
-Sodium is soluble so it dosent form a precipate and it mkaes a colourless solution
What happens when copper sulfate is added to sodium hydroxide and its equation?
-Copper(II)hydroxide a insoluble blue metal hydroxie is formed
Copper sulfate + sodium hydroxide -> cpper hydroxide + sodium sulfate
What colour precipitate does iron(II) and iron(III) produce in sodium hydroxide test?
Iron(II) - green
Iron(III) - orange-brown
What colour precipitate does copper(II) produce in sodium hydroxide test?
Copper(II) - blue
What colour precipitate do calcium and zinc produce in sodium hydroxide test?
Both white
How do you tell the difference between calcium and zinc in sodium hydroxide test?
-Both are white, but if you add excess NaOH zinc hydroxide dissolves to form a colourless solution wherreas calcium hydroxide dosen’t dissolve
Whats the basis for the sulfate ion test?
-Barium ions wil react with sulfate ions to produce a white insoluble barium sulfate
How do you do the sulfate ion test?
- First add dilute HCl to solution
- Then add a few drops of barium chloride solution, BaCl2
- If sulfate ions present, you get a white precipitate
Why do you add dilute HCl to the solution, when testing for sulfate ions before adding barium chloride?
-This is to remove and carbonate or sulfite ions in the solution as these are impurities that can also react with the barium ions
What is the basis for the carbonate ions test?
Hydrogen ions from dilute acids react with carbonate ions to produce carbin dioxide + water
2H+(aq) + CO3 2-(aq) -> CO2(g) + H2O(L)
You can test for the carbon dioxide wiht limewater test
What happens if dilute acid added to compound containing carbonate ions?
- If carboante ions present, gas bubbles will be produced
- If bubbed through limewater and limewater turns cloudy CO2 is present
What is the ion is the exception for the halide ion test and why is it an exception?
-Silver fluorde is soluble in water, so no precipitate is formed
How do you carry out the halide ion test?
- First add some dilute nitric acid, then few drops of silver nitrate
- The silver ions react with halide ions o form a silver halide precipitate
- e.g Ag+ + Br- -> AgBr
Why is dilute nitric acid added at the beginning to halide test and why isn’t hydrochloric acid added?
- Dilute nitric acid is used to get rid of any carbonate ions as they would produce a pale precipitate with silver nitrate confusing results
- Hcl can’t be added as it will add chlorine ions tosolution and that is what we are testing for
What are the results of halide ion test?
- Chloride gives white precipitate
- Bromide gives cream precipitate silver bromide
- Iodide gives a yellow precipitate silver iodide
