Group 7 Flashcards
Describe and explain the Group 7 trend in boiling points
The boiling point increases as you go down the group due to:
- increase in the size of the molecules
- increase in the number of electrons
- more chance of an instantaneous dipole
- greater (bigger) van der Waals’ between the molecules
Describe and explain the Group 7 trend in Electronegativity
decreases down the group due to :
- increase in the number of shells
- increase in atomic radii
- increase in the amount of shielding
- less attraction for the electron pair
Describe the physical appearance of each element in group 7
Fluorine = yellow gas
Chlorine = yellow-green gas
Bromine =red liquid
Iodine = grey solid
State the trend in the oxidising ability of the halogens and explain
Oxidising power decreases down the group due to :
- an increase in the number of electron shells
- increase in the atomic radii
- increase in the amount of shielding
- a decrease in the ability to attract an electron
What type of reaction proves the decreasing oxidising ability of halogens?
displacement reactions
Describe the colour of the solution when you react chlorine, bromine and Iodine to metal halides
Write the ionic equation for when chlorine is added to an aqueous solution of potassium bromide
Write the ionic equation for when chlorine is added to an aqueous solution of potassium iodine
Write the ionic equation for when bromine is added to an aqueous solution of potassium iodine
State the trend in the reducing power of the halides and explain
increases down the group :
- an increase in the number of electron shells
- an increase in the ionic radii
- an increase in the amount of shielding
- a decrease in the amount of attraction for the outer electron
- an increase in the ease of electron loss
This makes it easier for the halides to lose its electrons and donate it
What is the reaction between halide ions and silver nitrates used for?
to discover which halide ion is present
Describe how to carry out the reaction of halide ions with silver nitrate and how to carry out the subsequent tests used to distinguish them further
make the test solution by adding nitric acid to the sample and then adding silver nitrate solution dropwise
Subsequent tests: add some dilute ammonia solution dropwise until it is excess. After add concentrated ammonia solution dropwise until it is excess
Describe the results seen when halide ions react with silver nitrate
Fluorides produce no precipitate
Chlorides produce a white precipitate
Bromides produce cream precipitate
Iodides produce a pale yellow precipitate
Describe the results seen when halide ions react with dilute ammonia and concentrated ammonia
Florine= nothing
Chlorine = white precipitate dissolves, goes clear (soluble) in both
Bromide= insoluble in one, cream precipitate dissolves in concentrated ammonia (goes clear)
Idodine= insoluble in both
In what reaction is the trend in the reducing power of halides shown and how?
the increasing trend in the reducing power can be seen in the reactions of solid sodium halides with concentrated sulfuric acid
the halogen with the most reducing power is able to reduce the oxidation state of sulphur the most
What are the observations when sodium fluoride reacts with concentrated sulfuric acid? State the type of reaction that takes place, state the products and write the equation
Mistry white fumes
HF produced
Acid-base
2NaF + H2SO4 → Na2SO4 + 2HF
*
What are the observations when sodium chloride reacts with concentrated sulfuric acid? State the type of reaction that takes place, state the products and write the equation
Misty white fumes
HCl produced
Acid-base reaction
2NaCl + H2SO4 →Na2SO4 + 2HCl
What are the observations when sodium bromine reacts with concentrated sulfuric acid? State the type of reaction (s) that takes place, state the products and write the equation (s)
Misty white fumes = Acid -base = HBr produced
Colourles gas = redox = SO2 produced
Brown fumes = redox = Br 2 produced
Write the half equations for the redox reaction that takes place between sodium bromine and concentrates sulfuric acid
What are the observations when sodium Iodide reacts with concentrated sulfuric acid? State the type of reaction (s) that takes place, state the products and write the equation (s)
Misty white fumes = Acid -base = HI produced
Colourles gas = redox = SO2 produced
Yellow solid = redox = Sulfur produced
Bad egg smell= redox= H2S
Purple fumes = redox = I2 produced
Write the half equations for the redox reaction that takes place between sodium iodide and concentrates sulfuric acid
What does disproportionation mean?
when the oxidation state of some atoms of the same element increase and others decrease
How is chlorine used to make bleach? Write down the equation with the oxidation states.
Chlorine reacts with cold, dilute sodium hydroxide to form sodium chlorate(I), which is an oxidising agent and an active ingredient in household bleach
What is the equation for the reaction of chlorine with water? Write down the equation with the oxidation states of chlorine only.
cl2 = 0
HCLO = +1
HCL=-1
What is the equation for the reaction of chlorine with water IN THE SUNLIGHT? Write down the equation with the oxidation states of chlorine only.
What are the advantages and disadvantages of adding chlorine to drinking water?
pros:
- kills disease-causing microorganisms
- some chlorine persists in the water and prevents reinfection further down the supply
- prevents the growth of algae, eliminating bad tastes ad smells
- removes discolouration caused by organic compounds
cons:
- Chlorine reacts with organic compounds to form chlorinated hydrocarbons, many are cancer-causing (small risk compared to diseases like cholera)
- chlorine has is harmful when breathed in and liquid chlorine can cause chemical burns
Explain why dilute hydrochloric acid is not used to acidify the silver nitrate solution in the test for halide ions
HCl would form a white precipitate (due to the chloride ion it contains)
Give a reason why chlorine is not formed when solid potassium chloride reacts with concentrated sulphuric acid
sulphuric acid’s oxidising power is not strong enough
chlorine is a weak reducing agent
