HSC Chemistry Question Thread

[haony98]

Hi
Can someone explain molar heat of neutralisation
It's not an actual dot point in the syllabus but we will get tested on it and it's kinda a mix of of the concept of molar heat + neutralization reactions

[jakesilove]

Hi
Can someone explain molar heat of neutralisation
It's not an actual dot point in the syllabus but we will get tested on it and it's kinda a mix of of the concept of molar heat + neutralization reactions

Hey! I'm not sure I quite understand your question, but I think you're asking about the heat absorbed/released when an acid and a base react? This is sort of a dot point, and I have definitely seen marks allocated to this topic area. It's a really simple concept, and you don't need to know much about it.

At it's heart, every neutralisation reaction is exactly the same;


Now, it just so happens that this reaction is exothermic; ie. as the reaction moves forward, heat is released. In fact, for a strong acid and a strong, base, about 56kJ of energy per mole is released! Thus


Now, this is only every 'assessable' when it comes to the practicality of cleaning up large chemical spills etc. If you mix a large amount of base (say, NaOH) with a huge spill of acid (say, HCl) then a huge amount of energy can be released. This is dangerous for people nearby, for the region on which the spill has occurred, that sort of thing. Again, tiny tiny point in the syllabus, but sometimes assessed!

Key take aways:
1. Acid/Base neutralisation is always essentially the same reaction
2. That reaction is exothermic

Hope that all made sense! Great question

[beau77bro]

I love that you call him sir aha I do not miss High School

hshahahahah i full call all my teachers and everyone sir even the female teachers ahahahah, bad habit sorry. I AM GETTING A BOOK AND TAKING NOTES RIGHT NOW, THANKYOU JAKE,  always so helpful thankyou.


when i finish typing up the pracs from this and my prac work ill post and ask? in probably a billion years. but thankyou this will help so much, esp those titration notes. mint btw. which im worst at and will probably be the prac hhahahahah but thankyou again i actually cant thankyou enough.

[jakesilove]

hshahahahah i full call all my teachers and everyone sir even the female teachers ahahahah, bad habit sorry. I AM GETTING A BOOK AND TAKING NOTES RIGHT NOW, THANKYOU JAKE,  always so helpful thankyou.


when i finish typing up the pracs from this and my prac work ill post and ask? in probably a billion years. but thankyou this will help so much, esp those titration notes. mint btw. which im worst at and will probably be the prac hhahahahah but thankyou again i actually cant thankyou enough.

No problem, seriously glad the above helped. Let me know if you have ANY questions about anything I've posted, and of course I would be more than happy to take a look at notes you put together

[Wren]

hey hoping someone can clarify for me in the testing for anion prac my school says for the last step add Fe2+ in an alkaline solution to check if there is phosphate. I was just wondering why am I adding Fe2+

[jakesilove]

hey hoping someone can clarify for me in the testing for anion prac my school says for the last step add Fe2+ in an alkaline solution to check if there is phosphate. I was just wondering why am I adding Fe2+

Hey! If we add Iron ions (say that five times fast), we end up producing Iron phosphate, which is insoluble! So, to test for phosphate, if we add Iron ions and see the precipitation of a solid, we can be confident that Phosphate was present If we add excess iron, we can get all the Phosphate out!

[Yagami Light]

thanks guys

[jakesilove]

thanks guys

Glad you're finding the forum useful! Feel free to pop up a question anytime, and welcome!

[imda.beast]

hi jake, can you also run through the identifying different ions in solution practice and the main point I have to remember. it is for a prac exam, thank you

[jakesilove]

hi jake, can you also run through the identifying different ions in solution practice and the main point I have to remember. it is for a prac exam, thank you

Hey! Basically, you just need to remember your solubility rules/flame tests. Then, you'll likely be given a solution containing a number of ions. Use the solubility rules/flame test colours to figure out a way of determining each ion. There isn't much to this one in terms of prep, except you really do need to memorise the rules (Assuming they don't give them to you!). I've put the way I remember each rule below.




Let me know if I can add anything else!

[MisterNeo]

Hey! Basically, you just need to remember your solubility rules/flame tests. Then, you'll likely be given a solution containing a number of ions. Use the solubility rules/flame test colours to figure out a way of determining each ion. There isn't much to this one in terms of prep, except you really do need to memorise the rules (Assuming they don't give them to you!). I've put the way I remember each rule below.

(Image removed from quote.)
(Image removed from quote.)

Let me know if I can add anything else!

Isn't it spelled "mnemonic"? Pneumonic is a lung thing... 

[jakesilove]

(Image removed from quote.)
Isn't it spelled "mnemonic"? Pneumonic is a lung thing... 

This may very well be true...

[chelseam]

Let me know if I can add anything else!

The flame test one is the most brilliant thing I have ever seen

[RuiAce]

This may very well be true...

Rip.

The flame test one is the most brilliant thing I have ever seen

It's the whole basis of fireworks

[Wren]

Hey! If we add Iron ions (say that five times fast), we end up producing Iron phosphate, which is insoluble! So, to test for phosphate, if we add Iron ions and see the precipitation of a solid, we can be confident that Phosphate was present If we add excess iron, we can get all the Phosphate out!

Thanks Jake. And also I've seen another chart where barium is added. Is there any difference?