Hsc Marathon 2009 - Chemistry (2 Viewers)

[Kaatie]

just anything on the standards potential page which we dont have to remember for the exam

use an equation to show the formation of a condensation polymer, im really stuck on this one :S

 

[gurmies]

just anything on the standards potential page which we dont have to remember for the exam

use an equation to show the formation of a condensation polymer, im really stuck on this one :S

A general one would be:

R-OH + HO-R -----------> R-O-R + H2O

For cellulose formation:

HO-C6H10O4-OH + HO-C6H10O4-OH ------------> HO-C6H10O4-O-C6H10O4-OH + H2O

______________________________________________________________
Describe gamma decay

 

[Kaatie]

gamma decay is when a neutron bomards an element making it excited and excess energy is relieved by gamma ray emission, yes bad definition but my books dont have much about it

describe the structure of cellulose

 

[gifted:)]

OOft, this is a hard one to do! Ill try my best in answering. Cellulose is a polymer of which the monomer units are glucose. it can be writtten as OH-(C6H12O6)-OH.
when glucose molecules combine to form cellulose, the OH on the right -hand C atom of one molecule combines with the OH of the left-hand Carbon atom of the next glucose molecule.
- for bonding to occur alternate glucose units must be inverted

-this bonding produces a very linear molecule. the geometry of the rings and the C-O-C bond angles cause this linearity

Q. Describe how Radioisotopes are produced?

 

[shady145]

radioisotopes are made by alpha bombardment in nuclear reactors or but particle accelerators.

Q. what are some uses of petrochemicals?

 

[gifted:)]

Some typical uses of petrochemicals are:
- vinyl acetate for paint, paper and textile coatings vinyl chloride for
- polyvinyl chloride PVC)
- resin manufacture
- ethylene glycol for polyester - textile fibers
- styrene which is important in rubber and plastic manufacturing.

Q. what masses of lithium, zinc and cadium need to be oxidised to produce a mole of electrons?

 

[Kaatie]

no idea :S, is it in a particular topic or just a general question? (hint please )

 

[shady145]

cant zinc have 2 oxidation number, in which u would need to change the question. the thing that has me is what is 1 mole of electrons.
moles=mass/molecular mass
does that follow to say 1 electron is 1 mole of electrons?

 

[Kaatie]

yeah i have never heard of a 'mole of electrons', did you want to ask a question instead?

 

[shady145]

ok lol
describe the process of factional distillation

 

[Kaatie]

Its a process by which substances are vapourised and then condensed by cooling. with mixtures of liquids having similar boiling points multiple still heads in a fractioning collum condense and return some of the vapour several times with the more volatile liquids rising furthur up the collum before being drawn off

identify the term used to describe the process by which monomers are converted to a polymer

 

[marcquelle]

polymerisation?

 

[Kaatie]

yep

identify the chemicals used in the alkene/alkane bromine experiment and justify their choice

 

[gurmies]

Cyclohexane and Cyclohexene were used in the school laboratory as they are colourless and liquid at room temperature meaning changes can be observed easily? Bromine water was used at the removal of HOBr by Cyclohexene causes the rapid decolourisation whereas cyclohexane does not change the bromine water...pretty crappy answer but it's the best I can do with no study of chemistry these holidays =(

Link the branching of LDPE to it's low density on a chemical level

 

[Kaatie]

not sure :S

 

[bored of sc]

Link the branching of LDPE to it's low density on a chemical level

Not completely sure.

Since the chains are branched it means there is more space between neighbouring polymers. This implies there is a relatively low amount of matter from the polymer occupying a specific volume, hence a low density. In terms understandable, they are not packed closely together as the branched chains spread the neighbouring polymers apart further, leaving gaps of empty space.

Is that the kind of answer you are looking for?

 

[bored of sc]

New question: What is general formula for an alcohol? Justify your answer with an example e.g. ethanol.

 

[gifted:)]

Fractional distillation is used to separate mixtures of miscible liquids, such as ethanol and water. The process depends on the components of the mixture having different boiling points. The liquid is heated so that it turns into a gas. The vapours pass up a fractionating column where they are gradually cooled. As each of the components of the mixture cools to its boiling point, it turns back into a liquid. The different components of the mixture condense at different levels in the fractionating column and thus may be separated.

Q. what would be the average molar mass of cellulose that conatained on average 300 glucose units per molecule? What would be the mass of the glucose from which this cellulose had been formed?

P.s my previous question was from conquering chemistry-hsc course, roland smith. it was from chapter 2 electrochemistry, question 19 i was also confused

 

[gifted:)]

woops, sorry

 

[shady145]

C(n)H(2n+1)OH
ethanol.
C2H5OH

Q. describe a condensation reaction