Dekoyl's Questions

[dekoyl]

Oh shi-

Yeah it's "A 20 mL sample was made up to.." Is that the reason for ?

If so, with what wording would I use ?

Thanks

[chem-nerd]

3.13 x 10^-6 mol in 25mL aliquot

x10 to get n in 250mL diluted sample

/20mL to get concentration of undiluted sample


OR

calculate concentration in 25mL aliquot and x by dilution factor (250/20)

[TrueTears]

mol

mol

M





M

[dekoyl]

Bah - Thanks guys. I don't think I  was even trying to calculate the concentration when I did it
And I forgot the c1v1 = c2v2 formula as well

[dekoyl]

Do we often have 1,1-dichloroethane? Just that in this paper, they require us to draw it.
If my memory serves me right, I once learnt that we don't have 1,1-dichloroethane (can't remember the exact theory behind it).

Thanks

[TrueTears]

I'm not sure if 1,1-dichloroethane exists or not, but drawing shouldn't be too hard.

[dekoyl]

^Thanks TT I didn't have problems drawing it. It's just that when I drew it, I wondered if there could be such a thing.

[/0]

The Heinemann book has 1,1-dichloroethane as a product of substitution. 1-1-dimethylethane certainly can't exist though.

[dekoyl]

Do all nitrogenous bases of DNA have an amine functional group?
I thought amine was . All of them have it except thymine (which has ) but the answers imply thymine has an amine functional group as well.

[polky]

Do all nitrogenous bases of DNA have an amine functional group?
I thought amine was . All of them have it except thymine (which has ) but the answers imply thymine has an amine functional group as well.

From what I remember, amine is a side group that has a nitrogen attached to the carbon. (so what's attached to the nitrogen itself, other than the C, doesn't really matter)

[Mao]

Do all nitrogenous bases of DNA have an amine functional group?
I thought amine was . All of them have it except thymine (which has ) but the answers imply thymine has an amine functional group as well.

Primary Amine:

R-NH2

Secondary Amine:

R-NH-R'

Tertiary Amine:
   R"
   |
R-N-R'

[dekoyl]

Lisa Chem 2008 Q2(f)
I don't understand why they do:

[ryley]

The amount of NaHCO3 that reacts in d) will equal the amount of NaHCO3 produced by the reaction between Na2CO3 and HCl(reaction b) + the amount of NaHCO3 in the sample. So transposing this, the amount of NaHCO3 in the sample will equal the amount that reacts in d) - the amount produced by the reaction between NaH2CO3 and HCl(b again). I think when they refer to d), they're talking about the second titration. I don't think explained this well, if at all, but if you want I could scan my working for this question(I hate scanning stuff, so I think I'll relearn latex after exams)

[Mao]

b. phenolphthalein end point is where all Na2CO3 is converted to NaHCO3

Hence all Na2CO3 in the original aliquot is mol

c. 25.35 mL of HCl was used between the two end points, hence mol

d. basic -> acidic, look it up in data booklet

f. since all Na2CO3 was converted to NaHCO3, at the first end point,

Knowing from part c the amount of HCl consumed in reacting with ALL NaHCO3, and knowing from part b the amount of Na2CO3 you had originally, you can work out the amount of NaHCO3 you had originally and concentration

[dekoyl]

Just a confirmation..
Is it true that catalysts affect the reaction by having more particles have lower kinetic energy and uncatalysed reactions have a lower number of particles at higher kinetic energy?

That's one of the answers to Heinemann.