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Ask me for chemistry help! (2 Viewers)

Dylanamali

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Do you know your concepts well and understand it? or are you rote learning it? cos I know my classmates who does chem tutoring and they are unable to answer the questions where you need to conceptualise. mostly band 5/6 questions.

and guys I'm more than happy to help as well!!! message me if you need any
hi deloso, most of my knowledge has just come from understanding and not actually rote learning. I've actually done quite little learning from textbooks, booklets etc. I don't believe chemistry gets many questions where you need to 'conceptualise' can you provide me with a few examples? Thanks.
 

kittyful

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How would you answer this oxidation state question ... i kinda don't understand how you do these questions :(



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answer is B
 

Dylanamali

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how do i answer this question



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answer is a
Kittyful this graph works on the basis that a strong base + a strong acid = neutral salt, a strong base + weak acid = basic salt, a strong acid + weak base = acidic salt. When doing questions like this, where they present you with a graph, you want to look at the points where it drops, at the middle of this "dropping" is the equivalence point and the eq. point is indicative of the pH of the salt. In this case, if you get a rule and measure the midpoint of the dropping in the solid curve, you can notice that the midpoint is around 7, therefore the salt is neutral because of this we know that the reaction was between a strong base and strong acid (it could also be weak base weak acid), we then look at the dotted curve, and do the same method.. we measure the midpoint and notice it lies around 5. This shows that the salt is acidic and was therefore made from a strong acid and weak base. =)
 

_deloso

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hi deloso, most of my knowledge has just come from understanding and not actually rote learning. I've actually done quite little learning from textbooks, booklets etc. I don't believe chemistry gets many questions where you need to 'conceptualise' can you provide me with a few examples? Thanks.
that's good then.
I mean like questions that needs calculations given the scenario of an experiment in the question. or questions that are not straight out of the syllabubs dotpoints. I'll give you some examples later on though yeah. not today, busy studying lol yet I'm in BOS... the irony.
 

Dylanamali

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How would you answer this oxidation state question ... i kinda don't understand how you do these questions :(



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answer is B
In working with oxidation states you need to understand valency. When looking at the change in oxidation state of manganese we first start off by looking at MnO2. We know that the oxidation state of oxygen is -2 because of its valency, there are also 2 oxygens therefore oxygen is -4, to balance this manganese must be +4 as the overall charge of the compound is neutral. We then look at Mn2O3 - using the same method oxygen is -2, you times this by 3 and get -6, you have 2 manganese which have to equal +6 to balance this out. so one manganese must be +3. =)
 

Dylanamali

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that's good then.
I mean like questions that needs calculations given the scenario of an experiment in the question. or questions that are not straight out of the syllabubs dotpoints. I'll give you some examples later on though yeah. not today, busy studying lol yet I'm in BOS... the irony.
Ahh yeah fair enough, yeah some questions are quite challenging but my concepts are fairly well grounded. CSSA trial is tmoz, im hoping that its all doable =). good luck studying.
 

OmmU

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What are all the formulas we should remember? Exclude any that may be in options.
 

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by opening a bottle of coke, would i increase the temperature of the coke or decrease the temperature of coke and why?
 

Dylanamali

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by opening a bottle of coke, would i increase the temperature of the coke or decrease the temperature of coke and why?
Uh, wouldn't do anything to the temperature.. it would disrupt the equilibrium, releasing more CO2 gas.
 

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Uh, wouldn't do anything to the temperature.. it would disrupt the equilibrium, releasing more CO2 gas.
CO2(g) + H20(l) <==> H2CO3(aq)

wrong. it would decrease the temperature as the formation of carbonic acid is exothermic. so therefore by opening the bottle of coke you decrease the pressure and shift the equilibrium to the reactant side as it has more moles of gas. and as the reaction is exothermic, when u shift the equilibrium to the reactants side you decrease the temperature.

although the change in temperature would probably very very very very very small
 

Dylanamali

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wrong. it would decrease the temperature as the formation of carbonic acid is exothermic. so therefore by opening the bottle of coke you decrease the pressure and shift the equilibrium to the reactant side as it has more moles of gas. and as the reaction is exothermic, when u shift the equilibrium to the reactants side you decrease the temperature.

although the change in temperature would probably very very very very very small
hmm very nice explanation, I admit i was wrong.
Well done =)
 

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