Elements From The Sea Flashcards
Give the reaction of hydrogen bromide with conc. sulfuric acid
2HBr + H2SO4 -> SO2 + Br2 + 2H2O
Give the reaction for hydrogen iodide with conc. sulfuric acid
8HI + H2SO4 -> H2S + 4I2 + 4H2O
What alternative oxidising agent for sulfuric acid can be used to create pure HBr and HI?
Phosphoric acid
The thermal stability of the hydrogen halides _______ down the group
Decreases
When dynamic equilibrium has been reached, what happens to the concentrations and reactions rates?
The concentrations remain CONSTANT
The backward and forward reaction RATES EQUAL
What effects do the following factors have on the equilibrium constant? :
Pressure
Temperature
Concentration
Pressure -> no effect
Temperature -> will effect
Concentration -> no effect
What do half equations involve?
Transfer of electrons
Give the equation for the production of oxygen during electrolysis
4OH- -> O2 + 2H2O + 4e-
What are the physical states and colours of the halogens (Cl, Br, I) at room temperature?
Cl2 -> Pale green gas
Br2 -> Orange liquid
I2 -> Grey solid
What is the colour of iodine in aqueous solution, and in an organic solvent?
Aqueous -> Brown
Organic -> Purple
What three positive ions are always soluble?
Potassium, Sodium, Ammonium
What negative ion is always soluble?
Nitrate
What ions will form a precipitate with OH- ions? Give their colours
Cu2+ -> Blue ppt of Cu(OH)2
Fe2+ -> Green ppt of Fe(OH)2
Fe3+ -> Orange-brown ppt of Fe(OH)3+
What are the two major concerns about the danger of chlorine?
•Toxic to life
•Volatile; readily becomes gaseous
Give the equation for atom economy
% atom economy = (mr of desired product/mr of all products) × 100
What are the conditions for an ion to be reduced during aqueous electrolysis? Which electrode does this occur at?
Not part of group 1, 2 or Aluminium, occurs at the cathode
What are the conditions for an ion to be oxidised during electrolysis? What electrode does this occur at?
Must be a halide ion, occurs at the anode
Describe how you could investigate the relative reactivates of 1-iodo/chloro/bromobutane. Explain the results, giving relevant equations where appropriate
• Add equal volumes of each haloalkane to seperate test tubes
• Use same volume of ethanol as a co-solvent/universal solvent
• Add same volume of AgNO3 solution to 3 test tubes
• Place all test tubes in a water bath and give time for the temperatures to equilibriate
• Add the AgNO3 to the haloalkanes and time how long it takes for a precipitate to form/red cross method
• RX + H2O > ROH + H+ + X-
• Ag+(aq) + X-(aq) > AgX(s)
• Iodo will form a precipitate/obscure the cross fastest, and chlorine the slowest
•Reactivity is dependent on the bond enthalpy/strength; C-Cl is the strongest and C-I is the weakest
