Group 2 and Halogens Flashcards
What happens to reactivity down group 2?
It increases
Why does group 2 reactivity increase down the group?
Size of metal atom increases
Shielding increases
Outer electrons require less energy to remove
Since nuclear attraction decreases
What happens to alkalinity down group 2?
Increases
Why does group 2 alkalinity increase down the group?
Metal hydroxides are more soluble
So put more OH- into solution
What do metal hydroxides react with water to form?
White precipitate
What are group 2 compounds used for?
Indigestion
Agriculture
Medicine
What group 2 compound is used to treat indigestion?
Gaviscon - CaCO3
Why are group 2 compounds used in agriculture?
To treat acidic soil with alkaline
What group 2 compound is used to treat acidic soil?
Ca(OH)2 (known as lime)
Why are group 2 compounds used in medicine?
Insoluble so shows up in X-rays
What group 2 compound is used in medicine?
Barium (barium meal)
Metal + water?
Metal hydroxide + hydrogen
Metal + acid?
Metal salt + hydrogen
Metal + oxygen?
Metal oxide
Metal carbonate + acid?
Metal salt + water + carbon dioxide
Metal oxide + water?
Metal hydroxide
What is the appearance of F as a RT?
Pale yellow gas
What is the appearance of Cl as a RT?
Green gas
What is the appearance of Br as a RT?
Red-brown liquid
What is the appearance of I as a RT?
Grey solid
What is the appearance of F vapour?
Colourless
What is the appearance of Cl vapour?
Colourless
What is the appearance of Br vapour?
Orange vapour
What is the appearance of I vapour?
Purple vapour
Which is the most reactive halogen?
F
What happens to melting/boiling point down group 7?
Increases
Why does the melting/boiling point increase down group 7?
Halogen molecule size increases down the group
Greater London forces between molecules
So more energy needed to separate molecules
What happens to electronegativity down group 7?
Decreases
Why does electronegativity decrease down group 7?
Atomic radius increases
Shielding increases
Nuclear attraction reduced
Describe astatine
Radioactive
Strong oxidising agent
State at RT = solid
Electronegativity = lowest
What happens to reactivity down group 7?
Decreases
Why does reactivity decrease down group 7?
Atomic radius increases
Shielding increases
Nuclear attraction decreases
Gaining electrons = harder
Are halogens strong oxidising agents?
YES
Are the halogens the most reactive non-metals?
YES
What is cyclohexane (organic solvent) used for?
To distinguish between Br2 and I2
What are the three anion (negative ion) tests?
Carbonate
Sulfate
Halide
How do you test for carbonate ions?
Add dilute nitric acid to solid or solution
Bubble any gas made into limewater
What is the positive test for a carbonate test?
Cloudy
How do you test for sulfate ions?
Add dilute HCl
Add barium chloride/nitrate solution
What is the positive test for a sulfate test?
White precipitate
How do you test for halide ions?
Add dilute nitric acid
Add aqueous silver nitrate
What is the positive tests for a halide test?
Cl*- = white Br*- = cream I*- = yellow
What is the ionic equations for halide test?
Ag+ (aq) + Cl-(aq) —–> AgCl(s)
REPEAT FOR OTHER HALIDES
How do you further test for halide ions?
Add aqueous ammonia
What is the positive tests from the further halide tests?
Cl*- = soluble so precipitate redissolves Br*- = soluble so precipitate redissolves I*- = insoluble
What is the sequence for anion test?
Carbonate
Sulfate
Halide
Why is carbonate test done first?
As sulphates and halides don’t produce a gas with acid
Why is sulfate test done second?
To remove carbonates since barium carbonate can also produce a white precipitate
Why is halide test done last (third)?
To remove carbonate and sulfate as both insoluble in water
What is the test for cations (positive ions)?
Ammonium ions test
How do you test for ammonium ions?
Add aqueous NaOH
Gently warm
Hold warm litmus pH paper above
What is the positive test for ammonium ions?
Litmus pH paper turns blue
What does it mean that halogens act as oxidising agents?
Oxidises halide ion
Gains electrons
Reduced to form halide ion
What happens to oxidising ability down group 7?
Decreases
What is chlorine used to do?
Purify water
What are the risks associated with chlorine?
It’s toxic to humans so risks associated with gas leaks
What the formula for chloric (I) acid?
HOCl
What is the formula for bleach?
NaOCl Sodium chlorate
What is the equation for the production of chloric (I) acid?
Cl2 + H2O —-> HCl + HOCl
What is the equation for the production of bleach?
Cl2 + NaOH —-> NaCl + NaOCl + H2O
What are the ionic equations for the reactions?
2Br- (aq) + Cl2 (aq) —-> 2Cl- (aq) + 2Br2 (aq)
What colour is Cl2 water?
Colourless
What colour is Br2 water?
Yellow
What colour is I2 solution?
Orange/brown
What colour is Br2 in cyclohexane?
Orange
What colour is I2 in cyclohexane?
Purple/violet
Describe the colour changes in Cl2 water?
Cl2 - NO REACTION
Br2 - colourless —-> yellow Cl2 became KCl so water became yellow
I2 - colourless —-> orange/brown ^^^^^
Why does Cl2 have the strongest oxidising strength?
Has smallest atomic radius
Less shielding
So greater attraction for electron
What happens when Cl displaces KX?
Cl2 oxidises the X and reduces its self
Describe the colour changes in BR2 water?
Cl2 - colourless —-> yellow Br2 can’t displace Cl2 so NO REACTION and Br2 stays Br2 water
Br2 - NO REACTION
I2 - colourless —-> orange/brown Br2 can displace KI so I2 becomes I2 solution
Describe the colour changes in I2 solution?
Cl2 - colourless —-> orange/brown can’t displace so NO REACTION
Br2 - colourless —-> orange/brown ^^^^^
I2 - NO REACTION
In which reactions does displacement occur?
HINT: 3
Cl2 water with Br2 and I2
Br2 water with I2
