/0's Chem Questions

[/0]

lol that's interesting, thanks dekoyl and toothpick ;p

[chem-nerd]

be careful with the "complete evacuation" statement. as toothpick said, there will always be a small amount left in the tip and the pipette is calibrated to take this small volume into account.

there was a multiple choice question on this in one of the trial exams

[/0]

Give one chemical test that can be used to distinguish between Butan-1-ol and Butanoic acid.

Answers have: React with sodium carbonate.
But I said react both with ethanoic acid. The butan-1-ol solution will undergo esterification with the ethanoic acid, producing a sweet-smelling solution, while the butanoic acid won't produce a sweet smell. Is this acceptable?

[ed_saifa]

You answer does seem acceptable but while making the ester, errors might occur and you might not get the sweet smelling solution(personal experience). Making an ester isn't as simple as adding this and that.

[arthurk]

sulfuric acid required as well probably

[/0]

ah ok thx

gosh chemistry is hard lol

[/0]

How is this an acid-base reaction?

[methodsboy]

NaOH loses an proton --> behaves as an acid
H20 gains an proton --> behaves as a base (maybe they've separated the H30+ ion?)
someone confirm.

[/0]

Isn't acid-base to do with losing and gaining hydrogens?

[methodsboy]

^yeah. sorry i was in a hurry. you are write

[ed_saifa]

taken from my uni notes:

Lewis acid: any molecule or ion that can
form a new covalent bond by accepting a
pair of electron

Lewis base: any molecule or ion that can
form a new covalent bond by donating a
pair of electrons

[/0]

(maybe they've separated the H30+ ion?)
someone confirm.

hmm that's an interesting thought

taken from my uni notes:

Lewis acid: any molecule or ion that can
form a new covalent bond by accepting a
pair of electron

Lewis base: any molecule or ion that can
form a new covalent bond by donating a
pair of electrons

thanks but I don't know how that applies here


Also,

Which one of the following is least likely to be a product of a redox reaction between sulfuric acid and zing metal?
A.
B.
C.
D.

thx again

[chem-nerd]

How is this an acid-base reaction?

H₂O acts as an acid - donates a H to form OH^-

H(from NaH) acts as a base - accepts a H to form H₂

Also,

Which one of the following is least likely to be a product of a redox reaction between sulfuric acid and zing metal?
A.
B.
C.
D.

in H₂SO₄, S is in its highest oxidation state, +6

if you check the ONs for S in the options you should see that in SO₃ it is also +6 thus not a product of a redox reaction (and for H₂, its ON is now 0)

[ryley]

H2SO4 is a strong oxidant, so it is expected to be reduced. The O.N of Sulfur in H2SO4 is +6, so to find the least likely product, look for which option has the O.N of Sulfur equal to/higher than 6. In a), the O.N of Hydrogen is zero, and it is +1 in H2SO4, so this is likely. In b), the O.N of Sulfur is -2, again expected. In c), the O.N of Sulfur is 4, again a reduction. And in d), the O.N of Sulfur is 6, which is not a reduction, so I think answer is d).

EDIT: Sorry, didn't see above post.

[/0]

thx pr0s