24.5 redox and qualitative analysis Flashcards
what happens in the reaction between Fe2+ and MnO4-
Fe2+ is oxidised to Fe3+
MnO4- is reduced to Mn2+
what is the colour change when MnO4- is reduced?
purple to colourless
what happens when Fe3+ ions react with iodide ions?
Fe3+ is reduced to Fe2+
I- is oxidised to I2
what is the colour change when Fe3+ is reduced to Fe2+?
orange-brown to pale-green
what is the colour change when I- is oxidised to I2?
colourless to brown
what is the relationship between E value and reduction?
the more positive an E value is, the more likely reduction will occur in that reaction
what happens when Cr2O7 2- reacts with Zn?
Cr2O7 2- is reduced to Cr3+
Zn is oxidised to Zn2+
what is the colour change when Cr2O7 2- is reduced to Cr3+?
orange to green
what happens when Cr3+ reacts with excess Zn?
Cr3+ is reduced to Cr2+
what is the colour change when Cr3+ is reduced to Cr2+?
green to pale blue
what happens when H2O2 reacts with Cr3+ ?
Cr3+ is oxidised to CrO4 2-
oxygen is reduced
what happens when Cu2+ reacts with I- ?
I- is oxidised to I2
Cu2+ is reduced to Cu+
what colour change occurs when Cu2+ is reduced to Cu+ ?
pale blue to white precipitate
how are transition metal ions identified?
by adding NaOH and observing the colour changes
how are ammonium ions identified?
NaOH is added and solution is heated
turns red litmus paper blue
