Post your chemistry questions here. (1 Viewer)

[RANK 1]

its hsc soon and they say that teaching helps reinforce your knowledge.

so if you need help for chemistry post your question here or pm me and i'll answer it to the best of my ability. i do industrial chem so dont ask me questions regarding other options cos i wont be able to do them.

 

[kr73114]

The colourless aqueous solution of a white solid sample formed a precipitate with an acidified aqueous solution of lead (II) nitrate. What is the possible identity of the original
solution of this sample?

(A) copper (II) sulfate
(B) barium chloride
(C) sodium sulfate
(D) silver chloride

 

[RANK 1]

barium chloride solution is cloudy and silver chloride is a precipitate. which leaves A and C, but the question says colourless solution and anything with copper in it is blue so therefore its C

 

[RANK 1]

any1 else?

 

[JennaJameson]

help me i'm so shit at chem!!!

glucose is C₆H₁₂O₆

what is the mass of a polymer made up of 6969 glucose monomers???

 

[thoth1]

any1 else?

m8 can u keep this thread going, ill be posting questions 2moro. tnx.

 

[RANK 1]

help me i'm so shit at chem!!!

glucose is C₆H₁₂O₆

what is the mass of a polymer made up of 6969 glucose monomers???

wrong answer was here

 

[RANK 1]

although it just occurred to me that the mass of a glucose monomer does not equal the molar mass of glucose, so i dont really know whether or not you're supposed to times 6969 by the molar mass, as the mass of one glucose monomer would surely be alot less than the molar mass of glucose

 

[roryclifford]

although it just occurred to me that the mass of a glucose monomer does not equal the molar mass of glucose, so i dont really know whether or not you're supposed to times 6969 by the molar mass, as the mass of one glucose monomer would surely be alot less than the molar mass of glucose

Bro if its a polymer of that many Glucose monomers, wont that be Cellulose? So its 6969 x 180.068 - (1.008 x 2 + 16) x 6969 (so subtracting that many water molecules) ??, whatever that answer is.

 

[RANK 1]

yes it'll be cellulose but molar mass is 180.068 g/mol and the question asks for the mass of 6969 glucose monomers. mass of a monomer is different from molar mass

 

[RANK 1]

help me i'm so shit at chem!!!

glucose is C₆H₁₂O₆

what is the mass of a polymer made up of 6969 glucose monomers???

however i've just figured how to solve this question.

by using avogadro's number, 6.022 x 10^23 (prelim stuff) we can work out how many moles of glucose are in 6969 molecules of glucose.

n = 6969/6.022 x 10^23

n x 180.068 = 2.084 x 10^-18 g

 

[Bobbo1]

mate, avogadro's number has got NOTHING to do with this

 

[RANK 1]

mate, avogadro's number has got NOTHING to do with this

after criticizing someone you're suppose to show how you think its done, otherwise without backup, your criticism is worthless

 

[ohexploitable]

avogadro's numba is relevant

correct answer is 1.875 x 10^-18 g

 

[RANK 1]

avogadro's numba is relevant

correct answer is 1.875 x 10^-18 g

how did u get your answer?

 

[ohexploitable]

how did u get your answer?

6968 molecules of water are ejected since cellulose is a condensation polymer

 

[RANK 1]

damn... schoolboy error

 

[thoth1]

Can u explain to me how Ozone acts as both an upper atmosphere radiation shield and a lower atmosphere pollutant?

also plz explain what chlorine free radicals are and how they are formed from CFCs?

 

[RANK 1]

the ozone in the upper atmosphere absorbs uv radiation and converts its energy into chemical energy which is used to break the ozone up into an oxygen molecule and an oxygen free radical.
(i'd put equations, but i dont know how to insert subscripts)

the oxygen molecules also get broken up into 2 oxygen free radicals by UV radiation and the oxygen free radicals can also react with each other to form oxygen molecules.
anyways, the oxygen free radicals formed react with another oxygen molecule to form an ozone molecule. then the cycle repeats itself.

ozone in the lower atmosphere is responsible for photochemical smog. ozone is also toxic to living organisms, it causes respiratory problems, headaches and loads of other harmful effects. the ozone also forms oxygen free radicals which are highly reactive and damages organic molecules.

CFC molecules, like ozone reacts with UV and forms a free radical, the chlorine free radical. the chlorine free radical is basically just a chlorine atom with an unpaired electron, which makes it very reactive.

 

[thoth1]

the ozone in the upper atmosphere absorbs uv radiation and converts its energy into chemical energy which is used to break the ozone up into an oxygen molecule and an oxygen free radical.
(i'd put equations, but i dont know how to insert subscripts)

the oxygen molecules also get broken up into 2 oxygen free radicals by UV radiation and the oxygen free radicals can also react with each other to form oxygen molecules.
anyways, the oxygen free radicals formed react with another oxygen molecule to form an ozone molecule. then the cycle repeats itself.

ozone in the lower atmosphere is responsible for photochemical smog. ozone is also toxic to living organisms, it causes respiratory problems, headaches and loads of other harmful effects. the ozone also forms oxygen free radicals which are highly reactive and damages organic molecules.

CFC molecules, like ozone reacts with UV and forms a free radical, the chlorine free radical. the chlorine free radical is basically just a chlorine atom with an unpaired electron, which makes it very reactive.

tnx again. u r very gud at chem.