post the qustionFor those that do Industrial Chemistry, can you answer HSC 2010 Q32 (d) (ii)? The sample answer is too long for a 3 mark question like this...
We learnt that if you replace a strong acid into a weaker one it will require the same amount of volume to reach the equivalence point therefore the questions broken ?
Are you sure. I learnt the same as DrsoccerballNo it isn't, you will need 3 times more of the base in order to neutralise the 3 protons from the citric acid, in comparison to hydrochloric acid, which only requires enough base to neutralise the one proton donated. Remember, [HCl] = [H+] but 3x[C6H8O7] = [H+], when it is added to a base, such that all acid go through complete ionisation/donation of protons
Im not saying he is wrong, here are a few equations to illustrate my point:Are you sure. I learnt the same as Drsoccerball
So what does the amount of moles have to do with the total volume. We learnt that in titration replacing a strong acid with a weaker one would require the same volume ? IF its what you say theres a contradictionIm not saying he is wrong, here are a few equations to illustrate my point:
Citric Acid: C6H8O7 + 3NaOH -> (C6H5O7)3- + 3Na+ + 3H2O (This is because citric acid is a triprotic acid, and the addition of a base shifts the equilibrium for all 3 levels of disassociation)
Hydrochloric Acid: HCl + NaOH -> H2O + Na+ + Cl-
See how you require 3 moles of NaOH with citric acid, in comparison to hydrochloric acid. Plus the strength doesn't matter when it comes down to adding a base.
This is only applicable if both acids are monoprotic or diprotic etc.So what does the amount of moles have to do with the total volume. We learnt that in titration replacing a strong acid with a weaker one would require the same volume ? IF its what you say theres a contradiction
Yeah someone explained that to me thanksThis is only applicable if both acids are monoprotic or diprotic etc.
My answer would be that:Justify the continued use of the Arrhenius definition of acids and bases, despite the development of the more sophisticated Bronsted Lowry definition. (4 marks)
I've only learnt the Solvay process recently, but I'll have a go:Industrial Chem question: Assess both the importance and resulting environmental impacts of using limestone in the Solvay Process. (7 marks)
Just a few edits:I've only learnt the Solvay process recently, but I'll have a go:
Importance
Limestone (calcium carbonate, CaCO3) is an essential raw material for the production of sodium carbonate via the Solvay method. It is burnt/heated in a kiln in order to produce carbon dioxide gas and calcium oxide (lime), both of which are key elements in the Solvay process. Carbon dioxide gas is bubbled through ammoniated brine, participating in the reaction:
H2O(l) + CO2(g) + NH3(aq) + NaCl(aq) ---> NaHCO3(s) + NH4Cl(aq)
The sodium hydrogen carbonate is then heated to produce sodium carbonate (Na2CO3); thus carbon dioxide from limestone is an integral factor in allowing the production of Na2CO3. In addition, the lime produced by the limestone after heating is used to convert the left over ammonium chloride solution to more useful products (namely more ammonia).
Environmental impacts
Specifically, extraction of limestone from local deposits can alter the landscape from which it is taken, and may harm local ecosystems.
In addition, the Solvay process as a whole has several environmental impacts:
Calcium chloride (CaCl2) is a by-product and is not useful in the large quantities in which it is produced. Thus it is often disposed into waterways, which can greatly increase the concentration of chloride and calcium ions. This may disrupt marine ecosystems. In addition, the Solvay process is exothermic overall; this excess heat is released into the environment as thermal pollution and poses a real threat to ecosystems (particularly marine).
Moreover, while ammonia is theoretically completely recycled in the Solvay process, inevitably some of it is lost into the atmosphere where it acts as a pollutant.
Conclusion/Assessment
This, while limestone is a cheap raw material for the Solvay process, and is an important component in the process, its use does cause some environmental impacts, which can be minimised by careful monitoring and management and research into alternative methods of producing sodium carbonate.
1) In a 250 mL beaker mix 30 mL of NaOH and 10 mL of olive oil
Cheers dude, that's super helpfulJust a few edits:
For the first bolded part, you can take it further by talking about how lime is used to recover ammonia which is essential because ammonia is really expensive and recovering it will reduce overall costs.
For the second bolded part, you can take it further and talk about increase in salinity in soil because of the presence of chloride ions, and the increase in hardness of water which effectively kills off the ecosystem, if and only if, the CaCl2 is disposed in riverways. That is something you have to mention because most Solvay plants don't care about the disposal of CaCl2 and the thermal pollution associated with the combustion of CaCO3 because they dump it in oceans which has no overall environmental impact, but it has detrimental impacts on river systems. Also when you are talking about thermal pollution, its good to mention that it reduces the overall DO levels, potentially causing hypoxia of water and the destruction to the ecosystem.
Also a final thing to add in, there tends to be unburnt CaCO3 in the kiln which is disposed of into oceans. However if it was to be disposed into river systems, it will cause turbidity and has the potential to cause blockages of river systems.
I got one in my chem trial, so I don't see any reason there shouldn't be one in the HSCHas anyone seen any HSC questions asking about an experiment of galvanic cells?