Hsc Marathon 2009 - Chemistry (7 Viewers)

gurmies · Jan 17, 2009

Is it because the electrochemical reaction that occurs within some cells is not reversible - the ones that cannot be recharged?

Q: Explain why ethanol is a solvent for both polar and non polar substances

jackc91 · Jan 17, 2009

gurmies said:
Q: Explain why ethanol is a solvent for both polar and non polar substances

The hydroxy (OH) part of ethanol is polar becuase of the difference in electronegativity between O and H. As such it will dissolve polar substances. The alkyl chain is non polar as there is little to no difference in electronegativity between C-C and C-H. This means that ethanol can also dissolve non polar substances.

Q) Explain the displacement of metals from solution in terms of transfer of electrons

shady145 · Jan 17, 2009

in a displacement reaction a more reactive metal displaces that of a less reacitve metal. the more reactive metal is oxidised. e.g. Zn+SO4---Cu+ZnSO4
electron loss: Zn----Zn(2+)+2e-
electron gain:Cu(2+)+2e----Cu

Q. identify factors which can effect the equilibrium in a reversable reaction

scora · Jan 17, 2009

concentration, temperature, pressure
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shady145 · Jan 17, 2009

scora said:
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what topic is that in?

Pwnage101 · Jan 17, 2009

shady145 said:
what topic is that in?

Acdic?

shady145 · Jan 17, 2009

o i musnt be up to it yet, im around half way through acidic

hermand · Jan 17, 2009

is it sad that my teacher's so crap [we've done acids] that i have no idea what the answer to that question is.

i'm so changing classes this year. *fingers crossed* lol.

shady145 · Jan 18, 2009

ooo now i found it. did the dot point today.

buffers are solutions that help resist change in pH levels. Levels of pH need to be kept constant to allow normal procedures to occur.
e.g. in human saliva, the pH of the saliva must be around 6.4-7 or the amylase enzymes that help break down complex carbohydrates will not function.

Q. Describe some recent discoveries (in the last century) of elements

Kaatie · Jan 19, 2009

there are no futhur naturally occuring elements waiting to be discovered. Scientists are always trying to make new artificial elements which will be radioactive and remain in existance for a very short time, or may try and make artifical elements already invented by new means. So any of the radioactive elements eg technetium 99m, carbon-14, sodium-24

write an equation for the fermentation of glucose

aero135 · Jan 19, 2009

C6H12O6 (aq) ---------------> 2C2H50H(aq) + 2CO2 (g)

QUESTION: Outline the process involved in a titration

Kaatie · Jan 19, 2009

-rise burette with small amount of the solution of known concentration and discard
-overfill burette with this known solution and run the excess out. Solution level should be on 0.
-use pipette to measure a given volume of the solution of unknown concentration into a flask and place it under the burette
-add 2-3 drops of a suitable indicator to the flask
-put a white surface under the flask to make the end point easier to determine
-slowly run titrant into the flask swirling continuously. Near the equivalence point add the titrant drop wise until the indicator just changes colour and there is no furthur colour change
-read volume of titrant delivered on burette
-repeat 3 times and average
-calculate concentration

distinguish between the terms renew, reuse and recycle

minijumbuk · Jan 19, 2009

Outline the process of the production of LDPE and HDPE (6 marks)

shady145 · Jan 19, 2009

Kaatie said:
there are no futhur naturally occuring elements waiting to be discovered. Scientists are always trying to make new artificial elements which will be radioactive and remain in existance for a very short time, or may try and make artifical elements already invented by new means. So any of the radioactive elements eg technetium 99m, carbon-14, sodium-24

ok thats not answering the Q., describing how they were discovered during the last century. they were discovered in hydrogen bomb tests.
The energy given out by the blast was great enough to make heavier elements join together making a transuranic element.

aero135 · Jan 19, 2009

LDPE is produced by using high pressure and high temperatures and makes a polyehylene that is highly branched. HDPE is produced using high temperatures and low pressure and the use of a catalyst. It is linear and unbranching in structure.

QUESTION: Describe some properties and uses of a polymer either PVC or Polyestyrene

Kaatie · Jan 19, 2009

polystyrene
properties- hard, transparen. polystyrene foam is light and a good thermal insulator
uses-food containers, packaging, apple trays, TV cabinets, CD and casette cases and plastic cups

use an equation to show a substitution reaction

jackc91 · Jan 19, 2009

Substitution reaction: An atom or molecule replaces another atom or molecule.

eg) Zn <SUB>(s)</SUB> +<SUB> </SUB>CuSO<SUB>4 (aq) =======> </SUB>ZnSO<SUB>4 (aq) </SUB>+ Cu <SUB>(s) </SUB>
<SUB></SUB>
<SUB>Q) Describe the conditions under which a nucleus is unstable</SUB>

shady145 · Jan 19, 2009

the conditions where a nucleus is unstable are when the ratio of neurons

rotons is out of the stable zone. i dnt have a graph to show but its in my book lol.
the forces in the nucleus may be to powerful, e.g. if there are too many neutrons which will cause radioactive decay, where the extra neutron/s decay into a proton and electron.

Q. decribe an experiment you performed to produce ethanol by the process of fermentation.

gifted:) · Jan 20, 2009

shady145 said:
the conditions where a nucleus is unstable are when the ratio of neuronsrotons is out of the stable zone. i dnt have a graph to show but its in my book lol.
the forces in the nucleus may be to powerful, e.g. if there are too many neutrons which will cause radioactive decay, where the extra neutron/s decay into a proton and electron.

Q. decribe an experiment you performed to produce ethanol by the process of fermentation.

dissolve 20g of glucose in 250mL of water in a conical flask. have a delivery tube at the top passing into a beaker of limewater. weigh each seperately.
allow to stand for up to 5 days in a warm atmoshere (prefferebly an incubator 30-35 degrees) Reweigh both vessels at daily intervals and account for changes.
At the end of the 5 days do a fractional distillation of the flask contents. add porous pot first and do not exceed 95 degrees. to test distilate, ignite carefully in an evaporating basin.

question: Can uranium-235 be considered a transuranic element, even though it is involved in nuclear fission? (atomic bombs)

study-freak · Jan 20, 2009

gifted:) said:
question: Can uranium-235 be considered a transuranic element, even though it is involved in nuclear fission? (atomic bombs)

The definition of transuranic element is an element with an atomic number that is greater than that of uranium(i.e.Z>83). Thus, uranium is not transuranic.

Question: Identify a few examples of redox reaction.

Hsc Marathon 2009 - Chemistry (7 Viewers)

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