Predictions for Chemistry 2014 HSC? (3 Viewers)

[Hi there444]

When cleaning the spill of an unknown liquid (either acidic or basic), it is important to carefully chose a suitable chemical in order to minimise any damage. One such chemical that may be used is Sodium Hydrogen Carbonate (NaHCO3). This chemical is particularly useful in cleaning spills of acids and bases for multiple reasons.

Its ion HCO3- is amphiprotic, meaning it can donate or accept a proton, which is ideal for when the nature (acidity or basicity) of the spill is unknown, as it can neutralise either.

With the spill of the acid HCl
HCl + NaHCO3 <-> H2O + CO2 + NaCl

And in the spill of the base NaOH
NaHCO3 + NaOH <-> Na2CO3 +H2O

as seen in the above equations NaHCO3 neutralises both acids and bases.

NaHCO3 is a solid chemical, and can thus be contained easily.

It is non-toxic, and is thus safe to handle in school labs

Thus it can be seen that NaHCO3 is a suitable chemical to clean up acid and base spills



Is this even close to right?

Solid therefore can be contained itself and can absorb acid and base solutions.
Also:
You might want to consider: the fizzing can indicate the extent of completion allowing safety, heat of neutralisation is low hence less damage to surroundings since weak base.
I would say 4/5 (1-equations, 1- amphiprotic 1- evaluation 1-Property but the part of heat of neutralisation was important so you lost 1 there)

 

[enigma_1]

When cleaning the spill of an unknown liquid (either acidic or basic), it is important to carefully chose a suitable chemical in order to minimise any damage. One such chemical that may be used is Sodium Hydrogen Carbonate (NaHCO3). This chemical is particularly useful in cleaning spills of acids and bases for multiple reasons.

NaHCO3 contains HCO3- which is amphiprotic, meaning it can donate or accept a proton, which is ideal for when the nature (acidity or basicity) of the spill is unknown, as it can neutralise either acids or bases. This also makes NaHCO3 an amphoteric substance, allowing it to act as an acid or base.

With the spill of the acid HCl, NaHCO3 acts as a base, and according to the neutralisation reaction:
HCl + NaHCO3 <-> H2O + CO2 + NaCl

And in the spill of the base NaOH, NaHCO3 acts as an acidic substance:
NaHCO3 + NaOH <-> Na2CO3 +H2O

as seen in the above equations NaHCO3 neutralises both acids and bases.

Reasons for why NaHCO3 is suitable to be used to neutralise acid/base spills in lab:

NaHCO3 is a solid chemical, and can thus be contained easily.

It is non-toxic, and is thus safe to handle in school labs

Thus it can be seen that NaHCO3 is a suitable chemical to clean up acid and base spills

- NaHCO3 is a carbonate and when a carbonate reacts with an acid, it produces CO2 gas and so is will be more apparent when the reaction has stopped because the fizzing will also stop, allowing you to know when it is safe to handle the chemicals and remove them

- NaHCO3 is a weak acid/base and so upon neutralisation (which is exothermic) the heat released is far less than if it were a strong acid or base and hence it is safer, less risk associated withi it.

- NaHCO3 is a stable solid, readily available such as in baking powder

- NaHCO3 is easy to store

Disadvantages:

- for large spills, large amounts of NaHCO3 is required and it may not always be effective or enough

- The reaction is exothermic ie releases heat so may not be safe and care must be taken whilst conducting the procedure

- The salts produced could potentially be toxic and again care must be taken whilst handling them

Overall, the benefits outweigh the negtaives, and hence NaHCO3 is an effective substance to be used for neutralising acid/base spills.



Is this even close to right?

yeah it's quite good but right now is a 3/5
There are many more reasons, I've fixed up your answer above please see the bolded parts and hopefully it makes sense, as a complete answer

 

[enigma_1]

Also for your equations, I would do them differently. I really ceebs writing them up lol but w/e

HCO3- (aq) + HCl(aq) ----> H2CO3(aq) + Cl-(aq)

If you have time, talk about conjugates.

 

[enigma_1]

New question:

Assess the methods of sanitising and purifying mass water supplies and recent developments in these methods
(8 marks)

enjoy

 

[GOsie]

yeah it's quite good but right now is a 3/5
There are many more reasons, I've fixed up your answer above please see the bolded parts and hopefully it makes sense, as a complete answer

Solid therefore can be contained itself and can absorb acid and base solutions.
Also:
You might want to consider: the fizzing can indicate the extent of completion allowing safety, heat of neutralisation is low hence less damage to surroundings since weak base.
I would say 4/5 (1-equations, 1- amphiprotic 1- evaluation 1-Property but the part of heat of neutralisation was important so you lost 1 there)

Thanks for the feedback

 

[enigma_1]

Thanks for the feedback

No worries

 

[faisalabdul16]

New question:

Assess the methods of sanitising and purifying mass water supplies and recent developments in these methods
(8 marks)

enjoy

The purification of mass water supplies is a meticulous process which methodically clears water of any potential pollutants and ensures safe drinking water. The process involved are:
1) Screening - the mass water samples are passed through a massive sieve-like device which removes any large particles such as logs, dead farm animals (particularly at Waragamba dam) and other large debris. A physical process.
2) Aeration - the water is then either sprayed into the air to increase the dissolved oxygen concentration or repeatedly forced to move in a wave like movement to increase the dissolved oxygen content. Any iron in the water will be oxidised to form iron oxide, giving the water a metallic taste.
3) Flocculation - Chemicals such as alum are added to the water supply which coagulate suspended particles (note, not dissolved particles). These particles are not dissolved in the water but are present, floating around. The addition of alum causes the particles coagulate, forming an enormous clump which eventually settles at the bottom of the tanks.
4) Sedimentation - the water is then transferred into other tanks where sedimentation occurs. The water passes through and the sludge remains, which may be reused as fertilizer.
5) Filtration - The water undergoes filtration with small, fine particles of sand which try to only allow water particles through. This form of filtration also has charcoal filters, which removes colour and odours from the water. Hence the water at the end of this step should be colourless and odourless.
6) Chloridaion- filtered water is disinfected with the addition of chlorine which kills microorganisms present.
7) pH adjustment - chemicals such as ammonia are added to adjust the pH of water to about 7.
8) Fluoridation - fluorine is added to strengthen tooth enamel (1ppm).

Depending on which country an individual lives in, some use membrane filters.

CEEBS going into membrane filters, but, i would briefly talk about how it's made, why and why it isnt used, diagram of how it works.

Brain dump everything lol

 

[enigma_1]

The purification of mass water supplies is a meticulous process which methodically clears water of any potential pollutants and ensures safe drinking water. The process involved are:
1) Screening - the mass water samples are passed through a massive sieve-like device which removes any large particles such as logs, dead farm animals (particularly at Waragamba dam) and other large debris. A physical process.
2) Aeration - the water is then either sprayed into the air to increase the dissolved oxygen concentration or repeatedly forced to move in a wave like movement to increase the dissolved oxygen content. Any iron in the water will be oxidised to form iron oxide, giving the water a metallic taste.
3) Flocculation - Chemicals such as alum are added to the water supply which coagulate suspended particles (note, not dissolved particles). These particles are not dissolved in the water but are present, floating around. The addition of alum causes the particles coagulate, forming an enormous clump which eventually settles at the bottom of the tanks.
4) Sedimentation - the water is then transferred into other tanks where sedimentation occurs. The water passes through and the sludge remains, which may be reused as fertilizer.
5) Filtration - The water undergoes filtration with small, fine particles of sand which try to only allow water particles through. This form of filtration also has charcoal filters, which removes colour and odours from the water. Hence the water at the end of this step should be colourless and odourless.
6) Chloridaion- filtered water is disinfected with the addition of chlorine which kills microorganisms present.
7) pH adjustment - chemicals such as ammonia are added to adjust the pH of water to about 7.
8) Fluoridation - fluorine is added to strengthen tooth enamel (1ppm).

Depending on which country an individual lives in, some use membrane filters.

CEEBS going into membrane filters, but, i would briefly talk about how it's made, why and why it isnt used, diagram of how it works.

Brain dump everything lol

ahahah as usual, really well done!! I'm guessing you missed the assess part perhaps.
I'll just add it in incase people need help with it or something.

Meanwhile, here's a change to the previous question which addresses MMF specifically:

Describe and assess the use of Microscopic Membrane filtration in treating mass water supplies
(4 marks)

 

[faisalabdul16]

ahahah as usual, really well done!! I'm guessing you missed the assess part perhaps.
I'll just add it in incase people need help with it or something.

Meanwhile, here's a change to the previous question which addresses MMF specifically:

Describe and assess the use of Microscopic Membrane filtration in treating mass water supplies
(4 marks)

Yeah tbh, now that im studying english alot (alot as in 9 essays in 3 days along with memorising) i don't have time to surf BOS or write full answers to these chemistry questions. I'm barely answering the questions, so with this i thought i'd answer like 4 or 5 marks of it (as in the process of purification of water) and then leave the rest for someone so i can continue with English.

 

[enigma_1]

Yeah tbh, now that im studying english alot (alot as in 9 essays in 3 days along with memorising) i don't have time to surf BOS or write full answers to these chemistry questions. I'm barely answering the questions, so with this i thought i'd answer like 4 or 5 marks of it (as in the process of purification of water) and then leave the rest for someone so i can continue you with English.

lol yeah true, yeah that's fine.
I'm procrastinating so much on English lol.

btw thanks for reminding haha I always forget English is soo soon

 

[faisalabdul16]

lol yeah true, yeah that's fine.
I'm procrastinating so much on English lol.

Hahaha don't procrastinate, get off BOS!

This thread shall become more active than ever before, after the 4u and 2u maths exams. 5 days in between maths and chem

 

[enigma_1]

Hahaha don't procrastinate, get off BOS!

This thread shall become more active than ever before, after the 4u and 2u maths exams. 5 days in between maths and chem

truee, ok right after I finish this answer thing I'll do no more bos-ing for today haha
Hopefully I'll stick to this

 

[faisalabdul16]

truee, ok right after I finish this answer thing I'll do no more bos-ing for today haha
Hopefully I'll stick to this

hahaha im off for more english ttyl

 

[enigma_1]

The purification of mass water supplies is a meticulous process which methodically clears water of any potential pollutants and ensures safe drinking water. The process involved are:
1) Screening - the mass water samples are passed through a massive sieve-like device which removes any large particles such as logs, dead farm animals (particularly at Waragamba dam) and other large debris. A physical process.
2) Aeration - the water is then either sprayed into the air to increase the dissolved oxygen concentration or repeatedly forced to move in a wave like movement to increase the dissolved oxygen content. Any iron in the water will be oxidised to form iron oxide, giving the water a metallic taste.
3) Flocculation - Chemicals such as alum are added to the water supply which coagulate suspended particles (note, not dissolved particles). These particles are not dissolved in the water but are present, floating around. The addition of alum causes the particles coagulate, forming an enormous clump which eventually settles at the bottom of the tanks.
4) Sedimentation - the water is then transferred into other tanks where sedimentation occurs. The water passes through and the sludge remains, which may be reused as fertilizer.
5) Filtration - The water undergoes filtration with small, fine particles of sand which try to only allow water particles through. This form of filtration also has charcoal filters, which removes colour and odours from the water. Hence the water at the end of this step should be colourless and odourless.
6) Chloridaion- filtered water is disinfected with the addition of chlorine which kills microorganisms present.
7) pH adjustment - chemicals such as ammonia are added to adjust the pH of water to about 7.
8) Fluoridation - fluorine is added to strengthen tooth enamel (1ppm).

Depending on which country an individual lives in, some use membrane filters.

CEEBS going into membrane filters, but, i would briefly talk about how it's made, why and why it isnt used, diagram of how it works.

Brain dump everything lol

This is just about the effectiveness of each step.

1) Screening – is effective for its purpose however there is need for further treatment.
2) Aeration – the soluble iron and manganese salts are removed as they are oxidised to form precipitates which can be filtered out  getting rid of the metallic taste I think, not giving the water metallic taste. Again, aeration is
3) Flocculation – In the water, colloid particles are the cause of turbidity. Flocculation effectively removes these particles. Flocculation converts suspended particles into semi-solid or solid state. This is done by first adding lime to make the water basic and encourage the formation of ppts and then the addition of a floc such as Aluminium chloride. The coagulant/floc can then attract hydrogen ions and microorganisms. Then give an equation. Now flocculation is effective because it removes 99.9% of bacteria and 99% of viruses. It is also fast and cheap/.
4) Sedimentation – cheap and uses the natural process of gravity so is economically viabl, however its effectiveness may be hindered by the length of time required for sedimentation to occur.
5) Filtration – sand filtration using anthracite coal is more effective than the normal one because it is capable of removing odours, BUT extremely small particles are not removed, hence more treatment is necessary.
6) Chlroination – omg I’m actually getting bored of doing this hahah. 1998 Sydney water  protozoans such as Giardia and Cryptosporidium contaminated it so it means chlorination is not effective on its own in killing viruses. Lol now talk about MMF and the shit associated with it.
7) Fluoridation – good coz it strengthens tooth enamel and makes the water taste yummy 

K I’m outta here

sorry it looks retarded I wrote it on MS word and then pasted it here

hahaha im off for more english ttyl

oh good the fact that other people are actually doing English might encourage me to do so too!
Hahah cya )))))

 

[enigma_1]

For whenever you need a break from engrish

Describe the process of the industrial production of ethylene (4 marks)

 

[SuchSmallHands]

For whenever you need a break from engrish

Describe the process of the industrial production of ethylene (4 marks)

I don't study for English, so I'll take this one haha
The industrial source of ethene (sorry, I know the syllabus says ethylene but I hate that) is petroleum. There a numerous ways in which ethene can be obtained from petroleum.
- Fractional distillation: ethene is one of the fractions which make up crude oil (petroleum). It can be separated from the other fractions in petroleum in a fractionating column, which separates the hydrocarbons of which petroleum is composed based upon their respective boiling points.
- Cracking: to industrially produce further ethene, longer chain alkenes may be 'cracked' in order to decompose them in to a smaller alkane and alkene (such as ethene). Cracking may be done thermally, which involves the longer hydrocarbon fractions being passed through metal heated to 700-1000 degrees Celsius with vaporised H2O at a pressure of 7,000 kPa in order to decompose them. Cracking may also be done catalytically. Catalytic cracking involves heating the hydrocarbons to approximately 500 degrees celsius in the absence of oxygen and presence of an aluminosilicate zeolite catalyst in order to decompose them.

If you need a break, try: Explain the formation and effects of acid rain (5 marks)

Edit: probably should have added the 3 steps of initiation, propagation and termination and what each entails.

 

[Queenroot]

Initiation

 

[QZP]

Do you think they will ask on how SO2 / NOx is monitored? E.g. catalytic converters in car exhausts and scrubbers in power plants. Because I don't know much about the chemistry of them. Do you guys know???

 

[SuchSmallHands]

Do you think they will ask on how SO2 / NOx is monitored? E.g. catalytic converters in car exhausts and scrubbers in power plants. Because I don't know much about the chemistry of them. Do you guys know???

I don't know much on that either! I was thinking the same thing though. All I really know about how emissions of the oxides are managed are those two things that you've mentioned, and even then I can say that they exist and what their purpose is, but I can't go into much detail about their exact mechanisms for achieving that purpose.

 

[faisalabdul16]

Do you think they will ask on how SO2 / NOx is monitored? E.g. catalytic converters in car exhausts and scrubbers in power plants. Because I don't know much about the chemistry of them. Do you guys know???

I don't know much on that either! I was thinking the same thing though. All I really know about how emissions of the oxides are managed are those two things that you've mentioned, and even then I can say that they exist and what their purpose is, but I can't go into much detail about their exact mechanisms for achieving that purpose.

Is it in the syllabus?

Someone check?