Stopsign's Chemistry Marathon (2006) (1 Viewer)

[angmor]

probably was, i had that too. someone else answer this

 

[SL33pY]

Naturally occurring citric acid has the molecular formula c6h8o7. like all acids it reacts with carbonate solutions to form carbon dioxide gas. When 1.57g citric acid was added to a solution containing excess sodium carbonate 295ml carbon dioxide (25 and 103kPa) was formed.

a) write an equation for the reaction of hydrogen ions with carbonate ions. How many moles of Co2 formed?

aight wiggaz do this!

 

[angmor]

.295/24.79 = .011M of CO₂

 

[angmor]

my turn =


Calculate the pH of a solution formed when 0.5g of sulfuric acid is dissolved in 1400mL of pure water.

 

[Ioup]

Justify the use of concentrated Sulfuric Acid in esterification reactions.

 

[Riviet]

Calculate the pH of a solution formed when 0.5g of sulfuric acid is dissolved in 1400mL of pure water.

Wouldn't we need the molarity of at least one of the solutions to be able to calculate the pH?

 

[Ioup]

I'm gonna guess and say 1.4.lol/
Assuming the first ionisation only occurs.
-_o

 

[onebytwo]

Calculate the pH of a solution formed when 0.5g of sulfuric acid is dissolved in 1400mL of pure water.

sorry, im confused.
just in regard to the practically of this, is it even possible to have 0.5g of sulfuric acid, isnt it only an acid when its dissolved, i mean you cant have a solid acid can you?

 

[angmor]

dunno lol this was a question in the trial.
i think what you do is find the moles of sulfuric acid, then divide that by 1.4L of water to get your concentration.

 

[replayee]

yeh thats what you do because the reaction is h2so4 + h2o = h3o + hso4

therefore the number of moles of h2so4=no of moles of h30+

so assuming we dont care about none of this shitty diprotic business

its -log[5/FM of h2so4]

 

[rach1289]

i have a question from the 2004 HSC - Question 18 if your interested:
Analyse the relationship between the position of elements in the Periodic Table, and the acid–base behaviour of their oxides. worth 4 marks

 

[n@ttyb]

I think elements on the left, their oxides act basic... like Naoh.... im just guessing so feel free to correct me

 

[replayee]

metallic oxides are basic while non metal oxides are generally acidic but some are neutral.

@natty b --- naoh isnt an element DURRRRRRRRRRRRRRRRR

 

[ugly14]

left of table are basic and become more acidic as u move to the right of the table

 

[kazan]

asess the potential for ethanol as an alternative fuel.

 

[n@ttyb]

@natty b --- naoh isnt an element DURRRRRRRRRRRRRRRRR

lol did i right that

 

[replayee]

Ethanol is a viable alternative as a fuel in the near future due to the increasing relative scarcity of crude oil, the main current source for fuels.

Adv- Ethanol can be used up to 10-20% in existing car engines without modification(post 1986 vehicles) and increases the octane rating of petrol.
Ethanol could be seen as more "environmentally friendly" as its combustion products are equal to the products used in its creation ie c2h5oh => co2 + h20.
ETHANOL IS RENEWABLE!

Disadv- Pure ethanol cannot be used in existing engines and requires modification.
Although its more environmentally friendly in the combustion phase one must consider from a more realistic point of view the massive inputs of energy in the distillation process(from fossil fuels) outweigh this perspective. Solar energy perhaps could solve this problem.
Ethanol also has a lower heat of combustion per gram and therefore releases less energy than its crude oil counterparts.
At the present time there is also no real incentive to switch to ethanol as it is currently not cost-effective in relation the relative cheapness of crude oil.
Another factor in the use of ethanol, especially if crops are grown just to produce it, there needs to be considerable amounts of clearing/deforestation to grow the crops as well as the remaining smelly wastes after fermentation.

Next Q: Why are some elements created in a nuclear reactor while others in a cyclotron?

 

[2006hsc]

Next Q: Why are some elements created in a nuclear reactor while others in a cyclotron?

I think you mean "why are radioisotopes created in a nuclear reactor while others in a cyclotron?"
anyway..

Some radioisotopes cannot be created by bombarding electrons as the elements shells may be all full (ie all electron places are already taken).

Some radioisotopes need to be created by neutron bombardment. Cyclontrons cannot bombard a nucleas with neutrons as they have no charge.

There is another reason which i cannot remember. Someone will answer this...

Next Question - explain the process of making ethene into polyethene? (there are 2 processes, please answer with the easier one )

 

[n@ttyb]

isnt that the initiation, propagation and termination ?

 

[2006hsc]

i duno, someone please answer this!^ it was a 2005 hsc question