10.Group 7, the halogens Flashcards
Describe the trend in size of atoms going down group 7
- going down the group atoms get bigger
- each element has one extra filled main level of electrons
Describe the trend in electronegativity going down in group 7
- electronegativity is the power of an atom to attract shared electrons in a covalent bond
- going down the group electronegativity decreases
- atoms get bigger and more shielding, going down a group
- less nuclear attraction between halogen nucleus and shared electrons electrons in the covalent bond
Describe the trend in melting and boiling points going down in group 7
- increase as you go down a group
- larger atoms have more electrons
- larger van der Waal forces
Define volatile
Easily evaporated at normal temperatures
Which is more volatile chlorine or iodine
- the lower the boiling point the more volatile the element
- so chlorine is more volatile
Describe the trend in oxidising ability going down a group
- going down a group the oxidising ability decreases
- shielding and atom radii increases going down
- nuclear attraction decreases
- this reduces the ability for atom to attract (accept) electrons
How do halogens react with metal halides
By displacement reaction. Halide in the compound will be displaced by a more reactive halogen.
Write the ionic equation for the extraction of bromine from sea water
Cl2 (aq) + 2Br- (aq) —> Br2 (aq) + 2Cl- (aq)
Describe how iodine is extracted from kelp
- salts such as NaCl KCL and K2S04 are removed by washing with water
- residue is then heated with manganese dioxide and conc. sulfuric acid and iodine is liberated
Write the ionic equation for the extraction of iodine from kelp
2I- +MnO2 + 4H+ —-> Mn2+ + 2H2O +I2
Describe the trend in reducing ability going down a group
- going down a group the oxidising ability increases
- shielding and atomic radii increases
- reducing nuclear attraction
- this increases the ability for atom to lose (donate) electrons
What reactions shows the trend in reducing ability
Reaction of solid sodium halides with conc. sulfuric acid
Name a observation when conc. sulfuric acid is added to NaCl
Steamy fumes of hydrogen chloride
Name the solid product when conc. sulfuric acid is added to NaCl
Hydrogensulfate
Write the equation for when conc. sulfuric acid is added to NaCl
NaCl (s) + H2SO4 (l) —> NaHSO4 (s) + HCl (g)
Is the reaction between conc. sulfuric acid and NaCl a redox reaction
- no
- as no oxidation state has changed
- the chlorine ion is too weak a reducing agent to reduce the sulphur
What kind of reaction is the reaction between conc. sulfuric acid and NaCl
Acid-base reaction
Name a observation when conc. sulfuric acid is added to NaBr
Steamy fumes of hydrogen bromide and brown fumes of bromine
What colour is bromine gas
Brown
Describe two reactions that occur when conc. sulfuric acid is added to NaBr
- first sodium hydrogensulfate and HBr are produced in an acid-base reaction
- bromide ions are strong enough reducing agents to reduce sulfuric acid to sulfur dioxide
Write the equations for when conc. sulfuric acid is added to NaBr and what reactions they are
1) NaBr (s) + H2SO4 (l) —-> NaHSO4 (s) + HBr (g)
an acid base reaction
2) 2H+ +2Br- + H2SO4 (l) —-> SO2 (g) + 2H2O (l) + Br2 (l)
a redox reaction
Name a observation when conc. sulfuric acid is added to NaI
- steamy fumes of HI
- black solid of iodine
- bad egg smell of hydrogen sulfide
Describe two reactions that occur when conc. sulfuric acid is added to NaI
- first sodium hydrogensulfate and HI are produced in an acid-base reaction
- iodine ions are better reducing agents so reduce the sulfuric acid even further to sulfur dioxide sulfur and hydrogen sulfide are produced
Write the equations for when conc. sulfuric acid is added to NaI and what reactions they are
1) NaI (s) + H2SO4 (l) —-> NaHSO4 (s) + HI (g)
an acid base reaction
2) 8H+ + 8I- + H2SO4 (l) —-> H2S (g) + 4H2O (l) + 4I2 (l)
a redox reaction
