Chapter 3 - Elements From The Sea Flashcards
what is the appearance of fluorine at room temperature
yellow gas
what is the colour of fluorine gas
yellow
what is the appearance of chlorine at room temperature
pale green gas
what is the colour of chlorine gas
pale green
what is the appearance of bromine at room temperature
red liquid
what is the colour of bromine gas
orange
what is the colour of bromine in an aqueous solution
brown
what is the colour of chlorine in an aqueous solution
pale green
what is the appearance of iodine at room temperature
black solid
what is the colour of iodine gas
purple
what can you do to make it easier to distinguish between the halogens in solution
mix with cyclohexane solution
describe the test for halides
precipitation reaction with silver nitrate
whats the test for chloride ions
add silver nitrate and a white precipitate forms
add ammonia and ppt dissolves
whats the test for bromide ions
add silver nitrate and a cream precipitate forms
add ammonia and ppt partly dissolves
whats the test for iodide ions
add silver nitrate and a yellow precipitate forms
add ammonia and ppt doesnt dissolve at all
what is the rule for halogen displacement reactions
the halogen nearer the top of group 7 is a stronger oxidising agent and can displace the halogens lower down the table
definition of electrolysis
the process of breaking down compounds using an electric current
what are the rules at each electrode during electrolysis of aqueous solutions
at the cathode - if the metal is more reactive than hydrogen then H+ accepts electrons and hydrogen gas is given off
at the anode - if no halogen is present then OH- will give up electrons and form oxygen
what is the evidence that iodide ions are the strongest reducing agents compared to bromide and chloride
iodide reduces sulfate ions to H2S (from +6 to -2 oxidation state).
bromide only reduces from +6 to +4
chloride doesnt reduce it at all
what is dynamic equilibrium
when the forward rate of reaction = the backwards rate of reaction so the concentrations of reactants and products remain constant (only happens in a closed system)
what is a closed system
where no more molecules can enter or leave
what is the formula for equilibrium constant (Kc)
concentration of products/concentration of reactants
what is le chateliers principle
in an equilibrium, if you change the conditions the equilibrium position will shift to oppose the change that was made
what are the rules for equilibrium position for concentration, pressure, temperature and using a catalyst
- increasing the concentration of something will cause the equilibrium position to shift to the opposite side to oppose
- increasing overall pressure shifts the equilibrium to the side with fewer molecules
- increasing temperature shifts the equilibrium in the endothermic direction (+enthalpy change)
- using a catalyst doesnt have any effect on equilibrium position as it only speeds up the reaction
