HSC 2012-2015 Chemistry Marathon (archive) (7 Viewers)

[vilst3r]

re: HSC Chemistry Marathon Archive

Q) What qualities of a primary standard must be considered for titration?

 

[AnimeX]

re: HSC Chemistry Marathon Archive

Q) What qualities of a primary standard must be considered for titration?

- high molecular weight [in order to minimise error]
- constant mass over time when exposed to air [ie not hygroscopic]

Question:
1) a) what is the difference between an isotope and a radioisotope? [1 mark]
b) outline the advantages and disadvantages of an industrial radioisotope [3 marks]

2) a) what are the properties of an Arhenius acid [1mark]
b) what are the properties of a Davy acid [1mark]
c) would NH4+ be considered an acid in a) and b)? [1mark]

 

[vilst3r]

re: HSC Chemistry Marathon Archive

- high molecular weight [in order to minimise error]
- constant mass over time when exposed to air [ie not hygroscopic]

Yeah that's right, I would also note high purity and solubility

Question:
1) a) what is the difference between an isotope and a radioisotope? [1 mark]
b) outline the advantages and disadvantages of an industrial radioisotope [3 marks]

2) a) what are the properties of an Arhenius acid [1mark]
b) what are the properties of a Davy acid [1mark]
c) would NH4+ be considered an acid in a) and b)? [1mark]

1)a) Isotope are elements with different number of neutrons to protons and Radioisotopes are similar but they are unstable when neutron to proton ratio is outside of 1 and 1.5

b) Radioisotopes are effective in industries as that can be used to help monitor product quality, where radioisotopes like Strontium 99 measures thickness of paper and Sodium-24 detects pipe leakage. Cobalt 60 has improved the medical industry by treating cancer patients and improving health of humans. However the problems associated with radioisotopes are that they require careful monitoring, as some radioisotopes like Cobalt 60 are dangerous as the gamma ray can harm healthy cells. Staff members and associates also need occupational health checks and training when working with radioisotopes.

2) a) An acid that ionises to produce H+ ions
b) Acids contain oxygen based on observing nitric and sulfuric acid
c) NH+4 is Arhennius when reacts with water to produce OH-

Q) Describe the development of AAS and how it works (3 marks)

 

[someth1ng]

re: HSC Chemistry Marathon Archive

Yeah that's right, I would also note high purity and solubility



1)a) Isotope are elements with different number of neutrons to protons and Radioisotopes are similar but they are unstable- which is neutron to proton ratio outside of 1<x<1.5 and atomic number higher than 83
b) Radioisotopes are effective in industries as that can be used to help monitor product quality, where radioisotopes like Strontium 99 measures thickness of paper and Sodium-24 detects pipe leakage. Cobalt 60 has improved the medical industry by treating cancer patients and improving health of humans. However the problems associated with radioisotopes are that they require careful monitoring, as some radioisotopes like Cobalt 60 are dangerous as the gamma ray can harm healthy cells. Staff members and associates also need occupational health checks and training when working with radioisotopes.

2) a) An acid that ionises to produce H+ ions
b) Acids contain oxygen based on observing nitric and sulfuric acid
c) NH+4 is Arhennius when reacts with water to produce OH-

Q) Describe the development of AAS and how it works

The most important one is that it is of known composition and stable in air.

 

[someth1ng]

re: HSC Chemistry Marathon Archive

it's c?

Correct.

 

[ocatal]

re: HSC Chemistry Marathon Archive

Yeah that's right, I would also note high purity and solubility



1)a) Isotope are elements with different number of neutrons to protons and Radioisotopes are similar but they are unstable- which is neutron to proton ratio outside of 1<x<1.5 and atomic number higher than 83
b) Radioisotopes are effective in industries as that can be used to help monitor product quality, where radioisotopes like Strontium 99 measures thickness of paper and Sodium-24 detects pipe leakage. Cobalt 60 has improved the medical industry by treating cancer patients and improving health of humans. However the problems associated with radioisotopes are that they require careful monitoring, as some radioisotopes like Cobalt 60 are dangerous as the gamma ray can harm healthy cells. Staff members and associates also need occupational health checks and training when working with radioisotopes.

2) a) An acid that ionises to produce H+ ions
b) Acids contain oxygen based on observing nitric and sulfuric acid
c) NH+4 is Arhennius when reacts with water to produce OH-

Q) Describe the development of AAS and how it works

Acids containing oxygen is based on Lavoisier's theory. Davy proposed that acids contain replaceable hydrogen.

 

[vilst3r]

re: HSC Chemistry Marathon Archive

Acids containing oxygen is based on Lavoisier's theory. Davy proposed that acids contain replaceable hydrogen.

Oh god, I got mixed up. Then Davy proposed acid have hydrogen based on HCl, HF and etc.

 

[HeroicPandas]

re: HSC Chemistry Marathon Archive

Acids containing oxygen is based on Lavoisier's theory. Davy proposed that acids contain replaceable hydrogen.

There is conflict in this. Davy proposed that acids contain hydrogen, later on in life, Justus von Liebig reacted acids with metals and therefore conlcuded that acids contained 'replaceable' hydrogen (there is evidence in Jacaranda)

Would you say for Davy's theory now for the HSC? (believe in yourself? or trust Sir Liebig?)

 

[bangladesh]

re: HSC Chemistry Marathon Archive

1) Changing the amount of solid in an equilibrium has no effect as solids have a constant concentration, so if you increase conc. of calcium ions and hydroxide ions, the system will adjust to minimise the change (Le Chatelier's Principle), hence it will favour the reverse reaction to decrease the rise in conc of Ca2+ and OH- --> so more calcium hydroxide and less OH-/Ca2+

2) Equilibrium does not change

Why doesn't changing the amount of solids in an equilibrium have any effect?
I'm quite confused about this.

 

[Menomaths]

re: HSC Chemistry Marathon Archive

Why doesn't changing the amount of solids in an equilibrium have any effect?
I'm quite confused about this.

Changing concentrations only affects the equilibrium when the reactants/products are in gaseous or liquid state, not solid.

 

[HeroicPandas]

re: HSC Chemistry Marathon Archive

1) Changing the amount of solid in an equilibrium has no effect as solids have a constant concentration, so if you increase conc. of calcium ions and hydroxide ions, the system will adjust to minimise the change (Le Chatelier's Principle), hence it will favour the reverse reaction to decrease the rise in conc of Ca2+ and OH- --> so more calcium hydroxide and less OH-/Ca2+

2) Equilibrium does not change

Why doesn't changing the amount of solids in an equilibrium have any effect?
I'm quite confused about this.

dingos and donkeys are funny animals

 

[someth1ng]

re: HSC Chemistry Marathon Archive

Solids don't have an effect because they are in a different phase - they are effectively sitting there doing nothing.

 

[ColdLipstick]

re: HSC Chemistry Marathon Archive

Ummm... I guess no one has asked a Question, ill put one:

Outline and assess the effectiveness of methods used to purify and sanitize mass water supplies, Justifying the precipitate used to clarify the water.

 

[AnimeX]

re: HSC Chemistry Marathon Archive

Yeah that's right, I would also note high purity and solubility



1)a) Isotope are elements with different number of neutrons to protons and Radioisotopes are similar but they are unstable when neutron to proton ratio is outside of 1 and 1.5

b) Radioisotopes are effective in industries as that can be used to help monitor product quality, where radioisotopes like Strontium 99 measures thickness of paper and Sodium-24 detects pipe leakage. Cobalt 60 has improved the medical industry by treating cancer patients and improving health of humans. However the problems associated with radioisotopes are that they require careful monitoring, as some radioisotopes like Cobalt 60 are dangerous as the gamma ray can harm healthy cells. Staff members and associates also need occupational health checks and training when working with radioisotopes.

2) a) An acid that ionises to produce H+ ions
b) Acids contain oxygen based on observing nitric and sulfuric acid
c) NH+4 is Arhennius when reacts with water to produce OH-

Q) Describe the development of AAS and how it works (3 marks)

very nice,
for 1a I would also mention that radioisotopes are radioactive ie emitting of ionizing radiation or particles
2a, wasn't Lavosier the guy who proposed acids contained oxygen?
b) davy was acids contain replacable hydrogen (examples are correct)
c) i think you misread the question, so for a it wouldnt be an acid but in b it would be considered an acid.

 

[AnimeX]

re: HSC Chemistry Marathon Archive

Changing concentrations only affects the equilibrium when the reactants/products are in gaseous or liquid state, not solid.

Solids don't have an effect because they are in a different phase - they are effectively sitting there doing nothing.

http://www.digipac.ca/chemical/mtom/contents/chapter3/chap3_7_3.htm

how come here it works for solids aswell?
I think it works for solids but DOESN'T affect it if the others are gases and you're dealing with pressure

 

[Frie]

re: HSC Chemistry Marathon Archive

http://www.digipac.ca/chemical/mtom/contents/chapter3/chap3_7_3.htm

how come here it works for solids aswell?
I think it works for solids but DOESN'T affect it if the others are gases and you're dealing with pressure

Yeah, if the reactants and products are all gases in a closed system, by adding a solid, you are decreasing the volume of the system, hence an increase in pressure and causing the equilibrium to shift to the side with less moles of gas.

 

[abdog]

Re: HSC 2012 Chemistry Marathon

Now a big marker:
Evaluate the impact of industrial sources of sulfur dioxide and nitrogen oxides on the environment, making use of appropriate chemical equations. (7)[/QUOTE]

Industrial sources of sulfur dioxide and nitrogen oxides(NOx) have a huge impact on the environment. Sources for sulfur dioxide include the combustion of fossil fuels or the extraction of metals from sulfur rich ores and sources for NOx include power stations and engines in motor vehicles.

Sulfur dioxide forms sulfurous acid with water, causing acid rain:
SO2 + H20 ---> H2S03

Nitrogen dioxide as well, to form nitrous and nitric acid:
2NO2 + H20 ---> HNO3 + HNO2

Acid rain has a negative effect on the environment. It reacts with carbonate in marble urban structures and corrodes it, or destroys the shells of shellfish.

The increased combustion of fossil fuels after the Industrial Revolution also led to pollution of the environment due to increased release of Sulfur dioxide and NOx. This is apparent as the air quality in major cities(London) deteriorated.

Gas found in ice core samples in Antarctica has shown that levels of N20(an oxide of nitrogen) has increased by about 10%.

Photochemical smog, a direct indicator of excessive levels of NO2, affects visibility and ozone, found in the smog, is harmful to humans.

Evaluation: The impact SO2 and NOx on the environment is massive, and measures should be taken to reduce their concentrations in the atmosphere.

Not really sure about my evaluation and equations, but that's all I have.

A multiple choice question:
The molar heat of combustion of propane is given in the data book as 2200 kJ mol-1
What does this mean?

(A) 1 g of propane releases 2200 kJ of heat
(B) 44 g of propane releases 2200 kJ of heat
(C) 1 g of propane absorbs 2200 kJ of heat
(D) 44 g of propane absorbs 2200 kJ of heat

 

[HeroicPandas]

Re: HSC 2012 Chemistry Marathon

A multiple choice question:
The molar heat of combustion of propane is given in the data book as 2200 kJ mol-1
What does this mean?

(A) 1 g of propane releases 2200 kJ of heat
(B) 44 g of propane releases 2200 kJ of heat
(C) 1 g of propane absorbs 2200 kJ of heat
(D) 44 g of propane absorbs 2200 kJ of heat

B?

 

[abdog]

Re: HSC 2012 Chemistry Marathon

B?

Yes! Reason? Because I thought molar heat of combustion was defined as the amount of energy 1g of substance blah blah...?

 

[ForOneEon]

Re: HSC 2012 Chemistry Marathon

A multiple choice question:
The molar heat of combustion of propane is given in the data book as 2200 kJ mol-1
What does this mean?

(A) 1 g of propane releases 2200 kJ of heat
(B) 44 g of propane releases 2200 kJ of heat
(C) 1 g of propane absorbs 2200 kJ of heat
(D) 44 g of propane absorbs 2200 kJ of heat

(B)?
As for your long response, I don't think it's 5-7 marks yet.
Here's what I would do, in a nutshell.

- Outline sources of SOx and NOx (which you did, GOOD!)

- Give eqns for the formation of acid rain by hydration and/or oxidation of SOx and NOx
(You sort of did this, but the main sulfur-based acid is SULFURIC ACID. I think. Oxidise SO2 to SO3 then hydrate)

- Remember that acid rain has THREE main concerns. These are:
- Damages limestone, sandstone, marble-based structures, which are usually heritage structures (You did this, GOOD!)
- Causes the acidity of the soil to decrease, leading to less plants being able to grow at optimal rates, even dying.
- Same to aquatic ecosystems, where phytoplankton may only live within a certain pH range or else they stop photosynthesis.

- SO2 is a lung irritant, responsible for many deaths in the years of the London Smog during the IR. (GOOD JOB, you did this!)
- NO2 also contributes to smog, but of a different kind; PHOTOCHEMICAL SMOG, causing the formation of ozone in the troposphere. This hampers visibility and causes harm to humans due to the poison of ozone.

Gas found in ice core samples in Antarctica has shown that levels of N20(an oxide of nitrogen) has increased by about 10%.

This, I did not know. Keep it in your response, it's good!

And finally, your evaluation, which is just to wrap up, as you have done.
If I were to mark this, I think it would be 4-5 marks out of 7.

Now, for mine!
Assess the need to monitor levels of lead ions in substances used in society and describe appropriate technologies that can be used for such measurements. - [7 marks]