Chemistry New Syllabus Advice / Sample Answers by an Experienced HSC Tutor (1 Viewer)

[jazz519]

Thank you so much for the clarification! Also, just. A quick question; for properties like tensile strength and etc. are we meant describe how the intermolecular forces provide that feature, i.e. the Ziegler Natta process in HDPE helps straighten and provide longer chains resulting in higher tensile strength, or can we just list the properties? Because, I feel otherwise it would take a loong time to explain each feature. Thanks!

Nah it's fine to just talk about the properties and intermolecular forces directly (rather than having to say a certain process does it because that wouldn't really be answering the main part of the question which is the link between uses and properties)

 

[Arrowshaft]

Nah it's fine to just talk about the properties and intermolecular forces directly (rather than having to say a certain process does it because that wouldn't really be answering the main part of the question which is the link between uses and properties)

Thanks, Jazz!

 

[_Anonymous]

Hi Jazz, had a few more questions.

1) Which precipitation titration methods should we definitely know (would Fajan's method be one we need to know)?
2) For the last dot point of Mod 8, could they expect us to remember a specific process and write a whole 8 marker response to it? That is, if they specify a specific process within the question instead of a broader "evaluate the factors of a certain chemical process you have studied"?

 

[jazz519]

Hi Jazz, had a few more questions.

1) Which precipitation titration methods should we definitely know (would Fajan's method be one we need to know)?
2) For the last dot point of Mod 8, could they expect us to remember a specific process and write a whole 8 marker response to it? That is, if they specify a specific process within the question instead of a broader "evaluate the factors of a certain chemical process you have studied"?

for the precipitation titrations you dont really need to memorise a specific process, but rather if given data in a question be able to perform the calculation. Also, yes I would recommend you memorise a specific process (I would personally go for Haber Process)

 

[jazz519]

Tip: How to do questions where you are asked to find pH from combining different solutions

A calculation question that shows up for Module 6 a lot is finding the final pH after an acid and base solution is combined. This type of calculation requires a good understanding of limiting reagents. Below is a sample method to follow when answering these questions

 

[jazz519]

Bump

 

[frog0101]

Do we need to know additional polymers beyond those provided as examples in the syllabus? Also, we will to know the initiation - activation - propagation - termination process, and is there anything else we should know for the formation of addition and condensation polymers?

 

[jazz519]

Do we need to know additional polymers beyond those provided as examples in the syllabus? Also, we will to know the initiation - activation - propagation - termination process, and is there anything else we should know for the formation of addition and condensation polymers?

In terms of properties and uses of the polymers, no those are the only ones you need to know

Yes you do need to know the process. Make sure you remember the diagrams for the process, those make a better answer then just describing it in words

Other things you need to know as I outlined in the previous post are:
- Going from the polymer structure to the monomers if given a diagram of a polymer
- Going from the monomers to the polymer If given a diagram of the monomer
(both of those are really common multiple choice questions, in the past HSC syllabus which is basically identical to this one for the polymers section, they used to come up every 1-2 years
- Performing simple calculations to do with if I tell you the structure of a monomer and how many units were used, you need to be able to calculate the mass of the polymer

 

[_Anonymous]

For complexation reactions, do we memorise all the complex compounds that form? I'm unsure of which ones to remember.

 

[jazz519]

For complexation reactions, do we memorise all the complex compounds that form? I'm unsure of which ones to remember.

No you won't have to memorise anything like that. A lot of module 8 in that inorganic analysis bit is not really memorisation content (apart from solubility rules and the flame tests). It is more focused on drawing graphs i.e. AAS, colorimetry and uv-vis and then you do a calculation based on the graph you have drawn. You just have to understand the role of complexation reactions in these types of chemical analysis i.e. it allows you to make a compound that is normally unsuitable for analysis using colorimetry suitable for analysis, because it changes the oxidation state and therefore colour is enhanced. Aside from that just need to understand the basic parts of a complex ion such as the transition metal and ligand

 

[Arrowshaft]

Hey Jazz to what extent would we need to know our pracs like do we memorise all the quantities, or can it be reasonably quantitative. Also, do we need to memorise the pH ranges for indicators?

 

[jazz519]

Hey Jazz to what extent would we need to know our pracs like do we memorise all the quantities, or can it be reasonably quantitative. Also, do we need to memorise the pH ranges for indicators?

Hi you don't need to memorise exact quantities because not each experiment will do the same thing and it doesn't really matter most of the time because the trend you will see will be the exact same. But I would strongly encourage you to state numbers in your answers (just make them up on the spot to sound reasonable enough). Also, yes it is necessary you memorise pH ranges for the indicators, because questions such as select a suitable indicator for a titration requires knowledge of the relationship between the equivalence point and pH range of an indicator

 

[Arrowshaft]

Hi you don't need to memorise exact quantities because not each experiment will do the same thing and it doesn't really matter most of the time because the trend you will see will be the exact same. But I would strongly encourage you to state numbers in your answers (just make them up on the spot to sound reasonable enough). Also, yes it is necessary you memorise pH ranges for the indicators, because questions such as select a suitable indicator for a titration requires knowledge of the relationship between the equivalence point and pH range of an indicator

Thanks, so can you fudge the numbers to a certain extent? And what if the stochiometric ratios don’t match up for like a qualitative experiment but you just want to convey the ‘trend’, do you still get penalised?

 

[jazz519]

Thanks, so can you fudge the numbers to a certain extent? And what if the stochiometric ratios don’t match up for like a qualitative experiment but you just want to convey the ‘trend’, do you still get penalised?

Well for HSC experiment I can't really think of any that have requirement of meeting the molar ratios, like for instance when you do fermentation you will always end up adding way more glucose than you actually use because the yeast dies when ethanol concentration goes too high, bromine water experiment you add like 2 drops of bromine water. So yeah it doesn't really matter. Here's an example of how you should structure methods:

For bromine water experiment:
1) In a fume cupboard with absence of UV light add 2 mL of hexane and hexene in separate test tubes using a dropper.
2) Add 5 drops of amber bromine water to each test tube using a dropper and swirl. Observe any colour changes that occur
3) Safely dispose of solutions into a waste beaker.

So some things that I as a marker would be looking for are:
- Conditions (does the specific experiment have some type of conditions that the reaction must take place in. So in the above you can't do this experiment in UV light because then substitution reactions will happen. Other experiments where conditions are important include fermentation where you need anaerobic conditions)
- Quantities (just need to be rough numbers --> literally just check if they are there, doesn't matter how much just can't be anything crazy or unreasonable)
- Equipment that are used (how did you add solutions to the test tube --> dropper, how did measure temperature --> thermometer)
- Colours of compounds sometimes are important in experiments that have colour changes (amber bromine water)
- States what observation you are looking for (in this case observe any colour changes that occur. In other experiments this could be observe if any bubbling occurs, observe change in mass etc)

 

[Arrowshaft]

Well for HSC experiment I can't really think of any that have requirement of meeting the molar ratios, like for instance when you do fermentation you will always end up adding way more glucose than you actually use because the yeast dies when ethanol concentration goes too high, bromine water experiment you add like 2 drops of bromine water. So yeah it doesn't really matter. Here's an example of how you should structure methods:

For bromine water experiment:
1) In a fume cupboard with absence of UV light add 2 mL of hexane and hexene in separate test tubes using a dropper.
2) Add 5 drops of amber bromine water to each test tube using a dropper and swirl. Observe any colour changes that occur
3) Safely dispose of solutions into a waste beaker.

So some things that I as a marker would be looking for are:
- Conditions (does the specific experiment have some type of conditions that the reaction must take place in. So in the above you can't do this experiment in UV light because then substitution reactions will happen. Other experiments where conditions are important include fermentation where you need anaerobic conditions)
- Quantities (just need to be rough numbers --> literally just check if they are there, doesn't matter how much just can't be anything crazy or unreasonable)
- Equipment that are used (how did you add solutions to the test tube --> dropper, how did measure temperature --> thermometer)
- Colours of compounds sometimes are important in experiments that have colour changes (amber bromine water)
- States what observation you are looking for (in this case observe any colour changes that occur. In other experiments this could be observe if any bubbling occurs, observe change in mass etc)

Thank you so much, this was very helpful!

 

[erucibon]

Back titration question:
20.00mL of cloudly ammonia was pipetted into a 250mL volumetric flask. 100mL of 0.5866M HCl in excess was added. The volume was made up to 250mL with distilled water. A burette was filled with 0.1194M NaOH (standardised) solution. The HCl and ammonia solution was titrated with the NaOH, with the mean titre being 22.75mL.
The manufacturer of the cloudy ammonia claims that the detergent contains 45.2gL-1 ammonia as ammonium hydroxide (NH4OH).
a) Calculate the concentration in gL-1 of NH4OH in the cloudly ammonia sample
b) Provide possible explainations for differences between the calculated results and the manufacturers claims

Thanks Jazz

 

[jazz519]

Back titration question:
20.00mL of cloudly ammonia was pipetted into a 250mL volumetric flask. 100mL of 0.5866M HCl in excess was added. The volume was made up to 250mL with distilled water. A burette was filled with 0.1194M NaOH (standardised) solution. The HCl and ammonia solution was titrated with the NaOH, with the mean titre being 22.75mL.
The manufacturer of the cloudy ammonia claims that the detergent contains 45.2gL-1 ammonia as ammonium hydroxide (NH4OH).
a) Calculate the concentration in gL-1 of NH4OH in the cloudly ammonia sample
b) Provide possible explainations for differences between the calculated results and the manufacturers claims

Thanks Jazz

I feel like there is some info missing in this question. How much of that hcl excess solution is titrated against the naoh. Otherwise if it’s the whole thing you are going to get a crazy different number to the manufacturers one

 

[jazz519]

Just thought I’d let you guys know who post on here. I will be taking leave from this website for a while as I am quite tired and over worked at this point from tutoring and uni over the past year. I am not sure for how long I will be gone.

Before I leave, in a day or two when the paper is released to the public I will make a set of comprehensive solutions for 2019 HSC PAPER on here: https://boredofstudies.org/threads/chemistry-exam-thoughts-predictions.388986/

In my absence I encourage you to continue this thread by posting questions and answering them amongst yourselves. Also, if any people who just finished their HSC feel like they can help out answering the questions, I would encourage you to give back to this website the type of help it has provided you during your hsc year, as these helpful forums can only be sustained through the efforts of past students who are passionate about that particular subject. I wish all of you new students doing year 12 chemistry now good luck in your first set of upcoming assessments

 

[Hithcock]

Just thought I’d let you guys know who post on here. I will be taking leave from this website for a while as I am quite tired and over worked at this point from tutoring and uni over the past year. I am not sure for how long I will be gone.

Before I leave, in a day or two when the paper is released to the public I will make a set of comprehensive solutions for 2019 HSC PAPER on here: https://boredofstudies.org/threads/chemistry-exam-thoughts-predictions.388986/

In my absence I encourage you to continue this thread by posting questions and answering them amongst yourselves. Also, if any people who just finished their HSC feel like they can help out answering the questions, I would encourage you to give back to this website the type of help it has provided you during your hsc year, as these helpful forums can only be sustained through the efforts of past students who are passionate about that particular subject. I wish all of you new students doing year 12 chemistry now good luck in your first set of upcoming assessments

Honestly, this thread was such an amazing resource for me (and definitely for others!) in the past few months, especially in the past week. I can honestly say that I would not have performed at my best capabilities without this thread . Hopefully you will get better soon. Your efforts have definitely helped a large number of students on this forum!

 

[jazz519]

Honestly, this thread was such an amazing resource for me (and definitely for others!) in the past few months, especially in the past week. I can honestly say that I would not have performed at my best capabilities without this thread . Hopefully you will get better soon. Your efforts have definitely helped a large number of students on this forum!

Thanks a lot for the really kind words