17B.3 Flashcards
What factors complicate describing the colours of chromium compounds
- some compounds have different colours as solids and aq solutions
- the colour of the solution depends on the concentration
- the presence of oxygen in an aq solution can affect the colour observed
what is the reaction, reaction type, colour change when hexaaquachromium(iii) reacts with OH alkali
(sodium hydroxide is added until no further change
is seen) the rest is on page 203
when hexaamminechromium(iii) complex is dissolved in water what colour is shown
green not violet as the negatively charged hydroxide ions would react with the complex to form haxahydroxoCrarrate(III) complex
what is the reaction, reaction type, colour change when hexaaquachromuim(iii) reacts with ammonia used as an alkali
Page 203
what happens when we add excess aq OH to Triaquatrihydroxochromium(iii)
further deprotonation occurs and the green precipitate would then form a green solution, sometimes all of the H2O is taken from it the H+ when the OH is concentrated enough but when any further deprotonation occurs the solution will instantly go from green precipitate to green solution (reaction 204)
how can the deprotonation reaction of metal hydroxides ions be reversed (or any hydroxides ions)
by adding any acid since they are an amphoteric substance which show the nature of neutral complexes
what is the reaction, reaction type, colour change when Triaquatrihydroxochromium(iii)(iii) reacts with aq ammonia
page 204 note this precipitate is slow to dissolve in ammonia
what will happen to Hexahydroxocrarrate(III) complex when it’s in an alkaline solution and hydrogen peroxide is added to it, including the reaction, reaction type, and colour change involved
it would be very easy oxidised, the rest page 204
what is the colour of chromate(VI) ions (2CrO4^2-)
yellow
what is to note about chromate(VI) ions
even though it is complex it doesn’t have square brackets but that is just to make it easier for people ykkkk, so like btw this can go for anything so note it down
chromate(VI) are stable in
alkaline conditions
what happens when you add acid to a Chromate(VI) ions
colour change will occur form yellow to orange as dichromate(VI) ions form (this is very easily revisable just add alkali that’s why its at eq)
Dichrmate(IV) ions (Cr2O7^-2) are more stable in
acidic conditions
what is the reaction, reaction type, colour change that occurs when Zinc metal is added to dichromate(VI) ions in acidic conditions
page 204 (note it all happens in acidic conditions)
what is the colour of Cr^2+
blue
