Stopsign's Chemistry Marathon (2006) (4 Viewers)

[Petinga]

1. Describe the naming of esters and relate it to the reactants that produced it
the alkanol ends with yl instead fo anol
the alkanoic acid ends with oate instead of oic
e.g propanoic acid + ethnaol->ethyl propanoate + water

2. What indicators would be used in a strong acid weak base
The indicator would be methyl orange with ph range of pH3-4.4

3. Explain what is meant by strong and weak acids in terms of ionisation
A strong acid is one that completly dissociates into hydrogen ions in aqeous solution
e.g HCl + H20 ->Cl^(-1) + H30^(+1)
A weak acid is one that only partially dissociates into hydrogen ions in aqeious solution
e.g CH3COOH + H20 <-> CH3COO^(-1) + H30^(+1)

4. What is the use of acids as food additives
Acids are used as food additves to prevent the growth and reprodcution of dangerious parhtogens and imnhibit the decaya and breakdown of vegetable or foods. The acidic environemtn destroys pathogen or prevent spread. for example vinegar and citric acid used to preserve cucumbers and onions. However also used oit mainatan health such as ascorbic acid or vitamin C

5. Define Le Chateliers principle
Le Chateliers principle states that if the concentration of products and reactants in a chemical system at equilibrium are subjected to a change in conditions, the chemical system wil adjust to re-establish equilibrium in such a way to partially counteract any change such as temp, conc. and pressure/volme.

Question:
1.Describe saponifcation(Industrial chem students)
2. systemic name of vinyl chloride and styrene
3. define polymerisation
3. what is AAS anfd how does it work(i.e wat pricincple it relies on)
4. Describe expereimetn of soft drink decarbonation

 

[Naylyn]

Question:
2. systemic name of vinyl chloride and styrene
chloro ethene and ethynl benzene
3. define polymerisation
The process by which monomer units join together to form a long chain molecule called a polymer
3. what is AAS anfd how does it work(i.e wat pricincple it relies on)
AAS is a method of determining the concentration of different substances. It is based on the principle of absorbtion spectra which is the idea that each substance has certain wavelenghts that it will absorb. A light of the wavelengths that the sample being measured aborbs is shined into a sample, the sample will absorb the light based on the amount of the subsance being measured in the sample, the amount of light absorbed can be used to determine the concentration in the substance
4. Describe expereimetn of soft drink decarbonation.
Placed a can of softdrink on an electronic balance
opened the can
took measurements every 1 minute for the first 5 minute
took measurements every 5 minutes for 20 minutes
took measurement every 10 minutes for 30 minutes
left the can overnight and took measurement the next day

Questions
1. Describe the differences between the properties of O2 and the ozone free radicle and relate it to their structure
2. Describe the process of rusting(shipwrecks)
3. Describe the measures that can be taken to prevent rusting(shipwrecks)
4. How does a membrane filter work and describe their design
5. A chemist dissolves 50g of NaOH in 300mL of distilled water, calculate the pOH and pH of the solution

 

[Naylyn]

this was in last year paper. i didnt completely understand it . just hv a vague idea on this

The flow chart shows a series of steps involved in the production of ethyl butanoate.
glucose--->mixture containing ethanol--->pure ethanol--->ethyl butanoate

Describe the chemistry and procedure involved in each of these steps.

This question was answered a coupleof pages ago, page 8 I think.

 

[little master]

oh ok thanks

1)
Oxygen free Radical: 6 valence electrons (2 unpaired), Oxygen gas decomposed by UV light to form Oxygen Radicals, release 2 electrons as they are unpaired, only existbreifly and is very reactive
Oxygen Radical: Very Stable, reacts with other metals to form oxide , necessary for respiration

2.) Microscopic mmembranes have microscopic pores and the use of the appropriate filters can avoid the need to chemically treat the water. Ehe membrane is made from synthetic polymer whic is dissolved in a mixture of solvents. Water is made to flow across the membrane rather than through it, as this reduces the blockge factor. The size of the pores determine which sized particles or organsims pass through the membrane. The filters are Micro,Ultra and Nano Filtration.

are the answers sufficient to describe those two dot points?

 

[Naylyn]

It always depends on how many marks the question is really, I'd say that they are fine for 2 and 3 mark question but that you would need more for higher mark questions

 

[little master]

for q 5) Is the answer pH=13.4, pOH=14-13.4= 0.6???

 

[Naylyn]

I must admit that I posted that question without doing the calculation first...

[OH] = {50/(35.5 + 16 + 1.1)}/300mL
[OH] = 3.16mol/litre
pOH = -log[OH]
pOH = -.5

pH + pOH = 14
pH = 14.5

I think thats the answer

 

[little master]

I must admit that I posted that question without doing the calculation first...

[OH] = {50/(35.5 + 16 + 1.1)}/300mL
[OH] = 3.16mol/litre
pOH = -log[OH]
pOH = -.5

pH + pOH = 14
pH = 14.5

I think thats the answer

i thought scale is between 0-14. and also in 1st line of ur calculation i think u usd the Mwt of Na as 35.5 instead of 22.99.. can u pls write the eq!!

 

[little master]

yea

MOLES= 50/(39.99)=1.25
[OH]= 1.25/0.3
pOH=-log 4.16 = -.619

pH +pOH = 14
pOH= 14.62

yea i am gettin tht now...i dunno seems wrng though!!

 

[Naylyn]

my bad

[OH] = {50/(23 + 16 + 1.1)}/300mL
[OH] = 4.1666 mol/litre
pOH = -log[OH]
pOH = -.62

pH + pOH = 14
pH = 14.62

I hope I haven't made another mistake...

Well I know that concentrated forms of strong acids have pH's that are negative so i don't see why strong bases can't have pH's of greater than 14

 

[little master]

Well I know that concentrated forms of strong acids have pH's that are negative so i don't see why strong bases can't have pH's of greater than 14

cool i never knew tht!! thx

moving on with the questions

1) What range of tests are used to
-identify heavy metals pollutions of water
- Monitor possible eutrphication of waterways

2) Identify the process and the instruments that can b used to detect radiation