bio90

I am researching what happens when seeds germinate. What I seem to understand so far, is that a seed imbibes water, and this is what triggers of the subsequent stages...but what actually happens? I read that enzymes break down the storage compounds, but what is the significance of this? Also I have found out that copper ions are non-competitive inhibitors of amylase, so the stored starch in a seed cannot be broken down. Why would this affect the germination process?

So 6 iron(II) ions would be needed. I get this: Cr2O72- + 14H+ + 6Fe2+ --> 2Cr3+ + 7H2O + 6Fe3+

Goodness, I actually laughed reading the first article, who would have thought. I've never heard of Salvia either, and we're covering drugs in Biology at the moment, so I'm interested to know what it actually is?

Thanks, that's a great help, I have guessed then that the (unbalanced) reaction is: K2Cr2O7 + Fe(NH4)2(SO4)2 + 7H2SO4 → K2SO4 + (NH4)2SO4 + Cr2(SO4)3 + Fe2(SO4)3 + 7H2O But I have been fiddling around with it pretty much since your post and I can't balance it (feeble brain huh). I can manage to get the ammoniums andand everything else to balance, but never the sulphates. I couldn't seem to get enough of them on the left hand side, so I changed the H+ to H2SO4, but even so, I couldn't balance it..does it involve some pretty large numbers?

Still a bit clueless on the products. I've managed to find out this though, when potassium dichromate is reduced, this is the half equation: Cr2O72+ + 14H+ + 6e- --> 2Cr3+ + 7H2O And I think the H+ comes from the acidified solution that the potassium dichromate is in. And I think the formula for ammonium iron(II) sulphate is: Fe(NH4)2(SO4)2

NOx is an important natural fertilizer for plants, and is also created from ammonium compounds by nitrifying bacteria. But nitrates are very soluble, and only really of use when dissolved in the soil, when they are present in the atmosphere is when they begin to cause real problems.

Thanks Fredrik and Dr DNA some interesting ideas there. I have decided to investigate how wine is oxidised naturally, ie just by exposing it to air, and I will be using quantitative analytical methods like density weighing, back titration and colorimetry. But those ideas will be useful in considering extension tasks. I think we have reached the conclusion though, that it is acetobacter which causes the main oxidation of ethanol in wine. Thanks guys =]

I know that the potassium dichromate(VI) oxides the iron(II) to iron(III) but that's all :/

I need to work out the equation for the reaction between potassium dichromate(VI) and ammonium iron(II) sulphate, but I just don't know where to start...any pointers?

I should say first, that this is only an A Level investigation, and my chemical knowledge is a bit limited I will be using bottled wine, but I am afraid I do not know what primary or secondary fermentation is, or whether the case is normal or atypical. I did wonder whether 4 days would be long enough to see a significant difference, would you recommend longer?

Thank you Fredrik. The reason I ask is that I am conducting an investigation into how the ethanol concentration of red wine decreases over a period of 4 days, and I know this is due to oxidation, but I am trying to research what causes this oxidation. Apart from the oxygen, of course

Thanks for the reply. Bacteria? So it has nothing to do with metal ions like Copper and Iron? This research is proving to be quite misleading! So does the acetobacter convert directly to ethanoic acid? Or is there still the intermittent stage with ethanal?

I was taught that to oxidise an alcohol, you need to have an acidified solution of potassium(VI) dichromate. However, as far as I am aware, this is not present in wine. So what other catalyst is there that oxidises the ethanol present in wine? Thank you.

I think my teacher has discussed this with us before, I thought it was really interesting, but would like to know more about the implications of this mutation if you know more about it

I am interested to find out about filters when carrying out colorimetry. From what I can look up, it says that filters are used to 'select the appropriate wavelength of light'. I would like to know: 1. How do you choose the right filter? 2. How does the filter select the appropriate wavelength of light? 3. Why is this particular wavelength most appropriate? Any help would be so much appreciated thank you.