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    A Level Chem, O Level Chem + Phys / Bio @ BedokFunland JC
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    5,554 posts since May '05
  • Moderator
    A Level Chem, O Level Chem + Phys / Bio @ BedokFunland JC
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    5,554 posts since May '05
  • Moderator
    A Level Chem, O Level Chem + Phys / Bio @ BedokFunland JC
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    5,554 posts since May '05
  • Moderator
    A Level Chem, O Level Chem + Phys / Bio @ BedokFunland JC
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    5,554 posts since May '05
  • Moderator
    A Level Chem, O Level Chem + Phys / Bio @ BedokFunland JC
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    5,554 posts since May '05
  • Moderator
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    • Originally posted by Light5:

      Do you have any advice as to how to study reaction mechanisms for Inorganic chemistry (any book,webisite,etc) that can be of help?


      Books to recommend for A Level Chemistry (in particular Inorganic Chemistry) :

      http://www.infinity.usanethosting.com/Tuition/#Books_for_H2_Chemistry

      Inorganic Chemistry Made Easy by George Chong KL

      Understanding Advanced Chemistry Through Problem Solving : Physical and Inorganic Chemistry by Jeanne Tan and Kim Seng Chan

      Understanding Advanced Physical Inorganic Chemistry : The Learner's Approach by Jeanne Tan and Kim Seng Chan

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    • Originally posted by Light5:

      Q5.) What could be the products and the mechanism for the following reaction :

      NO2 + H2O = ...?

      All i can predict is that nitric acid will be formed as NO2 is an acidic oxide however, that does not balance the equation so what will be the other product?


      Oxides of nitrogen are a complicated and messy affair, and for A level purposes, Cambridge would likely provide in-context hints if such is asked.

      The competent and astute A level candidate would notice that the OS of N in NO2 is +4, but yet the OS of N in the common N containing acids HNO2 and HNO3 (Latin names : nitrous and nitric acid; Stock names : nitric(III) and nitric(V) acids) are +3 and +5, which should lead you to a reasonable deduction that this isn't a straightforward case of hydrolysis of an electrophilic covalent oxide to generate an aqueous acid in which the OS of the heteroatom is conserved, as would usually be the case, eg. CO2 + H2O --> H2CO3, or SO3 + H2O --> H2SO4. At the very least, Cambridge would expect the competent and astute A level candidate to suggest the existence of a disproportionation reaction, and Cambridge more than likely would provide in-context hints within the question as to the exact identities of the products and intermediates (see links below).

      If you're interested in a more in-depth look into this reaction (it's entirely possible Cambridge might provide some of the following info in a data based question, and query the A level candidate accordingly across several related topics in the A level syllabus, possibly even asking for the reaction mechanism to be drawn out, ala Singapore-Cambridge A level 2012 P3 Q3), you can check out :
      http://pubs.rsc.org/en/content/articlelanding/2003/cp/b208564j#!divAbstract
      http://www.researchgate.net/publication/234036456_The_Heterogeneous_Hydrolysis_of_NO2_in_Laboratory_Systems_and_in_Outdoor_and_Indoor_Atmospheres_An_Integrated_Mechanism

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    • Originally posted by Light5:

      Q5.) What could be the products and the mechanism for the following reaction :

      NO2 + H2O = ...?

      All i can predict is that nitric acid will be formed as NO2 is an acidic oxide however, that does not balance the equation so what will be the other product?


      Oxides of nitrogen are a complicated and messy affair, and for A level purposes, Cambridge would likely provide in-context hints if such is asked.

      The competent and astute A level candidate would notice that the OS of N in NO2 is +4, but yet the OS of N in the common N containing acids HNO2 and HNO3 (Latin names : nitrous and nitric acid; Stock names : nitric(III) and nitric(V) acids) are +3 and +5, which should lead you to a reasonable deduction that this isn't a straightforward case of hydrolysis of an electrophilic covalent oxide to generate an aqueous acid in which the OS of the heteroatom is conserved, as would usually be the case, eg. CO2 + H2O --> H2CO3, or SO3 + H2O --> H2SO4. At the very least, Cambridge would expect the competent and astute A level candidate to suggest the existence of a disproportionation reaction, and Cambridge more than likely would provide in-context hints within the question as to the exact identities of the products and intermediates (see links below).

      If you're interested in a more in-depth look into this reaction (it's entirely possible Cambridge might provide some of the following info in a data based question, and query the A level candidate accordingly across several related topics in the A level syllabus, possibly even asking for the reaction mechanism to be drawn out, ala Singapore-Cambridge A level 2012 P3 Q3), you can check out :
      http://pubs.rsc.org/en/content/articlelanding/2003/cp/b208564j#!divAbstract
      http://www.researchgate.net/publication/234036456_The_Heterogeneous_Hydrolysis_of_NO2_in_Laboratory_Systems_and_in_Outdoor_and_Indoor_Atmospheres_An_Integrated_Mechanism

      Edited by UltimaOnline 01 Aug `15, 4:56AM
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    • Q1. No worries about focusing on Group vs Period, just do your best to *understand* (with use of mechanisms whenever possible; ie. you can attempt drawing out the mechanisms for most, if not) all of the inorganic reactions required by your own A level syllabus, instead of blind memorization. Make sense of it in your own way (eg. by use of analogies), own it for yourself.

      Q2. HX does indeed react in a nucleophilic substitution reaction with alcohols (you can attempt to draw the mechanism for this... fact is, online help via forums is by its nature limited, it's not feasible for me to draw out all the mechanisms you may be interested in; I can and will do this for my own tuition students when they're physically present, but it's not feasible and too time-consuming to do this online... if you're really interested in learning how to draw mechanisms for all A level reactions organic and inorganic, you might want to consider engaging a private tutor, in whichever country you're residing in).

      Nucleophilic substitutions of HX with RX can and does occur (of course, this is only meaningful with two different halides are involved), with the position of equilibrium favoring the thermodynamically more stable species; specifically the species with the stronger C-X covalent bond (ie. a more effective head-on or end-on overlap by less diffused electron orbitals to form a stronger sigma bond results in a more exothermic bond formation enthalpy).

      However, a twist to this was given in the Singapore-Cambridge 2013 A levels P3 Q1, in which (if you have access to the Singapore A level papers, you might like to check this out) the strongly exothermic (thus thermodynamically favorable) lattice formation enthalpy involved in the ionic precipitation of the lower Ksp sodium halide in propanone (polar aprotic) solvent, together with shifting of position of equilibrium as predicted by Le Chatelier's principle, results in R-I generated at the expense of R-Cl, despite R-Cl being a stronger covalent bond.

      However for aldehydes and ketones, any nucleophilic addition of the halide ion will be followed by it's elimination (the mechanism for nucleophilic acyl substitution is addition-elimination) to re-generate the aldehyde or ketone, as the halide ions are good leaving groups due to their low anionic charge densities (as opposed to say, hydride ions from LiAlH4 or alkyl nucleophiles from Grignard reagents).

      As for any potential Bronsted-Lowry acid-base reactions between HX and alky halides or aldehyde/ketones, alkyl halides and aldehyde/ketones aren't Bronsted-Lowy basic to begin with (aldehydes and ketones are actually slightly Bronsted-Lowry acidic, as the conjugate bases generated by the deprotonation of their alpha protons, are stabilized by having their negative formal charges delocalized by resonance over both the alpha C atom and the electronegative carbonyl O atom of the enolate ion conjugate base... if you're up for the challenge, draw the mechanism between both resonance contributors and elucidate the resonance hybrid).

      Q3. This is simultaneously a redox reaction as well as a Bronsted-Lowry acid-base reaction. It is a first and foremost a redox reaction because Mg is oxidized to Mg2+, and H+ from the acid is reduced to H2 gas. It is secondarily a Bronsted-Lowry acid-base reaction because HCl (if in aqueous state, more precisely hydroxonium chloride) is being deprotonated to generate it's conjugate base the chloride ion (or more precisely, water and the chloride ion) and thus generating the salt MgCl2(aq). For a P1 MCQ, choose the best option (psychologically profile the Cambridge setter's intentions if you're able to). For a P2 or P3 qn (or whatever equivalent in your syllabus), give *both* descriptive alternative answers with qualifying explanations to secure full credit.

      Q4. Every year, many students routinely ask, "is there a shortcut to drawing all possible isomers?". The short answer is : no there isn't. There can be systematic approaches (it's up to you to formulate your own), but there's no magical shortcut to drawing all possible isomers, especially when stereoisomerism (optical and geometrical) is also to be considered.

      But there is indeed a method (in fact, this is the *only* correct method, though it's far from being a shortcut) to reliably identifying any repeated structures. That's to name each of your structures. If they've the same name, then they're the same molecule.

      No problem Light5. Go ahead and feel free to continue asking your questions from both your CIE A level syllabus, as well as from Singapore Prelim papers. Though when quoting questions from past CIE papers or Singapore Prelim papers, it'll be preferred if you can provide the (eg. http://papers.xtremepapers.com) links to not only the question paper, but to the mark scheme as well (whenever available), for the sake of efficiency and convenience.

      Originally posted by Light5:

      Q1.)Thanks alot, couldnt have even thought of bronsted lowry theory for Q2..do you have any advice as to how to study reaction mechanisms for Inorganic chemistry(any book,webisite,etc) that can be of help? Instead of the Period 3 chlorides,oxides and group2,group 7 chapters, should i learn more compounds formed by period 3 elements and their corresponding reactions and if so, which ones should i focus on?

      Q2.) I know that HBr is an acid and Br, being more electronegative than H, has a partial negative charge..Also, Br has few lone pairs on it...if this is the case why cant HBr participate in a nucleophilic substitution or nucleophilic addition reaction with halogenoalkanes and aldehydes/ketones respectively?

      Q3.) How is Mg + 2HCL = MgCl2 + H2 an acid- reaction? I know that HCl is giving out H+ ions, but it isnt donating these protons to Mg, in fact it is donating Cl- ions to Mg...so how does this reaction stand true with bronsted-lowry acid-base theory?

      Q4.) Is there any general strategy for drawing correct structural isomers ensuring that none of them are repeated...how can i do this on a piece of question paper(since we dont get a rough sheet for the MCQ paper 1). Even if you can demonstrate it with an example, that will be fine?

      Again, thank you for answering my questions. I know my queries arent as advanced as those of singapore students but some of these misconceptions have arised while solving CIE past year questions...i will start asking questions related to singapore prelim papers once i start solving some of the difficult P1 and P3s. 


      Edited by UltimaOnline 01 Aug `15, 4:38PM
  • Moderator
    A Level Chem, O Level Chem + Phys / Bio @ BedokFunland JC
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    • Q1. No worries about focusing on Group vs Period, just do your best to *understand* (with use of mechanisms whenever possible; ie. you can attempt drawing out the mechanisms for most, if not) all of the inorganic reactions required by your own A level syllabus, instead of blind memorization. Make sense of it in your own way (eg. by use of analogies), own it for yourself.

      Q2. HX does indeed react in a nucleophilic substitution reaction with alcohols (you can attempt to draw the mechanism for this... fact is, online help via forums is by its nature limited, it's not feasible for me to draw out all the mechanisms you may be interested in; I can and will do this for my own tuition students when they're physically present, but it's not feasible and too time-consuming to do this online... if you're really interested in learning how to draw mechanisms for all A level reactions organic and inorganic, you might want to consider engaging a private tutor, in whichever country you're residing in).

      Nucleophilic substitutions of HX with RX can and does occur (of course, this is only meaningful with two different halides are involved), with the position of equilibrium favoring the thermodynamically more stable species; specifically the species with the stronger C-X covalent bond (ie. a more effective head-on or end-on overlap by less diffused electron orbitals to form a stronger sigma bond results in a more exothermic bond formation enthalpy).

      However, a twist to this was given in the Singapore-Cambridge 2013 A levels P3 Q1, in which (if you have access to the Singapore A level papers, you might like to check this out) the strongly exothermic (thus thermodynamically favorable) lattice formation enthalpy involved in the ionic precipitation of the lower Ksp sodium halide in propanone (polar aprotic) solvent, together with shifting of position of equilibrium as predicted by Le Chatelier's principle, results in R-I generated at the expense of R-Cl, despite R-Cl being a stronger covalent bond.

      However for aldehydes and ketones, any nucleophilic addition of the halide ion will be followed by it's elimination (the mechanism for nucleophilic acyl substitution is addition-elimination) to re-generate the aldehyde or ketone, as the halide ions are good leaving groups due to their low anionic charge densities (as opposed to say, hydride ions from LiAlH4 or alkyl nucleophiles from Grignard reagents).

      As for any potential Bronsted-Lowry acid-base reactions between HX and alky halides or aldehyde/ketones, alkyl halides and aldehyde/ketones aren't Bronsted-Lowry basic to begin with (aldehydes and ketones are actually slightly Bronsted-Lowy acidic, as the conjugate bases generated by the deprotonation of their alpha protons, are stabilized by having their negative formal charges delocalized by resonance over both the alpha C atom and the electronegative carbonyl O atom of the enolate ion conjugate base... if you're up for the challenge, draw the mechanism between both resonance contributors and elucidate the resonance hybrid).

      Q3. This is simultaneously a redox reaction as well as a Bronsted-Lowry acid-base reaction. It is a first and foremost a redox reaction because Mg is oxidized to Mg2+, and H+ from the acid is reduced to H2 gas. It is secondarily a Bronsted-Lowry acid-base reaction because HCl (if in aqueous state, more precisely hydroxonium chloride) is being deprotonated to generate it's conjugate base the chloride ion (or more precisely, water and the chloride ion) and thus generating the salt MgCl2(aq). For a P1 MCQ, choose the best option (psychologically profile the Cambridge setter's intentions if you're able to). For a P2 or P3 qn (or whatever equivalent in your syllabus), give *both* descriptive alternative answers with qualifying explanations to secure full credit.

      Q4. Every year, many students routinely ask, "is there a shortcut to drawing all possible isomers?". The short answer is : no there isn't. There can be systematic approaches (it's up to you to formulate your own), but there's no magical shortcut to drawing all possible isomers, especially when stereoisomerism (optical and geometrical) is also to be considered.

      But there is indeed a method (in fact, this is the *only* correct method, though it's far from being a shortcut) to reliably identifying any repeated structures. That's to name each of your structures. If they've the same name, then they're the same molecule.

      No problem Light5. Go ahead and feel free to continue asking your questions from both your CIE A level syllabus, as well as from Singapore Prelim papers. Though when quoting questions from past CIE papers or Singapore Prelim papers, it'll be preferred if you can provide the (eg. http://papers.xtremepapers.com) links to not only the question paper, but to the mark scheme as well (whenever available), for the sake of efficiency and convenience.

      Originally posted by Light5:

      Q1.)Thanks alot, couldnt have even thought of bronsted lowry theory for Q2..do you have any advice as to how to study reaction mechanisms for Inorganic chemistry(any book,webisite,etc) that can be of help? Instead of the Period 3 chlorides,oxides and group2,group 7 chapters, should i learn more compounds formed by period 3 elements and their corresponding reactions and if so, which ones should i focus on?

      Q2.) I know that HBr is an acid and Br, being more electronegative than H, has a partial negative charge..Also, Br has few lone pairs on it...if this is the case why cant HBr participate in a nucleophilic substitution or nucleophilic addition reaction with halogenoalkanes and aldehydes/ketones respectively?

      Q3.) How is Mg + 2HCL = MgCl2 + H2 an acid- reaction? I know that HCl is giving out H+ ions, but it isnt donating these protons to Mg, in fact it is donating Cl- ions to Mg...so how does this reaction stand true with bronsted-lowry acid-base theory?

      Q4.) Is there any general strategy for drawing correct structural isomers ensuring that none of them are repeated...how can i do this on a piece of question paper(since we dont get a rough sheet for the MCQ paper 1). Even if you can demonstrate it with an example, that will be fine?

      Again, thank you for answering my questions. I know my queries arent as advanced as those of singapore students but some of these misconceptions have arised while solving CIE past year questions...i will start asking questions related to singapore prelim papers once i start solving some of the difficult P1 and P3s. 


      Edited by UltimaOnline 01 Aug `15, 4:37PM
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    • Hi Light5, welcome to the forum! :)

      Q1. Even if you suspect Br2 may be formed as a possible intermediate (in the reduction of BrCl, which may be conceptualized as Br+ and Cl-, with OSes of +1 and -1 respectively), but knowing full well (as required by the A level syllabus) that the redox reaction between Br2 and I- is (of course) thermodynamically feasible under standard conditions, you should always give the final equation with the final product of the completed reaction, ie. in effect acknowledging that any Br2 formed (eg. as possible intermediate) would be further reduced to Br- by I- (which is in turn oxidized only to I2... any further oxidation would require a stronger oxidizing agent, and clues would be given in the question).

      Q2. If you (ie. as an A level candidate) correctly understand the nature of metal hydrides, you'll understand that it consists of the metal cation and the hydride anion H-, which being highly unstable (due to the high anionic charge density due to small ionic radius exacerbated by the low electronegativity of H) is thus a strong Lewis base (ie. strong nucleophile and strong Bronsted-Lowry base), and hence readily abstracts a proton from water (which you should be aware is a protic species) to generate H2 gas, leaving behind the metal hydroxide as the by-product (not to be confused with side-product).

      Edited to add : The forward reaction is favored both thermodynamically (due to positive entropy change) as well as by Le Chatelier's principle (due to gaseous product leaving the solvated reaction mixture).

      If your understanding and familiarity of reaction mechanisms (more commonly employed in organic chemistry, but chemistry is chemistry, and mechanisms are actually every bit as relevant to inorganic chemistry, despite the lack of exposure in this area for all A level students, whether international or Singapore) is strong, you're advised to draw out the mechanism for this (and other inorganic chemistry) reactions, which will enable you to truly understand (rather than just blindly memorize) why and how such reactions occur, and as such also helps you to correctly determine the identity and structure of the products.

      Feel free to continue posting your A level Chem qns here all the way till your A levels at the end of the year, Light5! ;)

      Edited by UltimaOnline 01 Aug `15, 7:15AM
  • Moderator
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    • Light5 asked :

      Hi, i am studying Cambridge Internation A level chemistry and have found that the questions asked are easier but very similar to the H2 chemistry papers. And as CIE is increasing the difficulty of papers each year, the questions will be more like the ones in the singapore prelim papers. Hence, i would like to ask questions that i have found tricky and difficult from both CIE and H2(i cant even solve some of the H2 prelim questions). 

      Q1:)

      Please look at Q3(d)(iii) of the following paper

      http://papers.xtremepapers.com/CIE/Cambridge%20International%20A%20and%20AS%20Level/Chemistry%20(9701)/9701_w13_qp_23.pdf

      How will i know what products will be formed when BrCl reacts with KI....i know its supposed to be displacement reaction but how can i be sure that KBr and KCl will be formed instead of Br2.....

      Q2.) Similarly, how would i know the products of the reaction of NaH(sodium hydride) with water if i only that MgH,NaH both react with H2O to give the same colourless guess?

      Is there any general way of knowing the products of chemical reactions such as above in keeping the fact that we know all the reactions of the chapter of periodicity(such as chlorides and oxides with water,etc)?

      Thank You for answering!

  • Moderator
    A Level Chem, O Level Chem + Phys / Bio @ BedokFunland JC
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    5,554 posts since May '05
    • Hi Light5, welcome to the forum! :)

      Q1. Even if you suspect Br2 may be formed as a possible intermediate (in the reduction of BrCl, which may be conceptualized as Br+ and Cl-, with OSes of +1 and -1 respectively), but knowing full well (as required by the A level syllabus) that the redox reaction between Br2 and I- is (of course) thermodynamically feasible under standard conditions, you should always give the final equation with the final product of the completed reaction, ie. in effect acknowledging that any Br2 formed (eg. as possible intermediate) would be further reduced to Br- by I- (which is in turn oxidized only to I2... any further oxidation would require a stronger oxidizing agent, and clues would be given in the question).

      Q2. If you (ie. as an A level candidate) correctly understand the nature of metal hydrides, you'll understand that it consists of the metal cation and the hydride anion H-, which being highly unstable (due to the high anionic charge density due to small ionic radius exacerbated by the low electronegativity of H) is thus a strong Lewis base (ie. strong nucleophile and strong Bronsted-Lowry base), and hence readily abstracts a proton from water (which you should be aware is a protic species) to generate H2 gas, leaving behind the metal hydroxide as the by-product (not to be confused with side-product).

      Edited to add : The forward reaction is favored both thermodynamically (due to positive entropy change) as well as by Le Chatelier's principle (due to gaseous product leaving the solvated reaction mixture).

      If your understanding and familiarity of reaction mechanisms (more commonly employed in organic chemistry, but chemistry is chemistry, and mechanisms are actually every bit as relevant to inorganic chemistry, despite the lack of exposure in this area for all A level students, whether international or Singapore) is strong, you're advised to draw out the mechanism for this (and other inorganic chemistry) reactions, which will enable you to truly understand (rather than just blindly memorize) why and how such reactions occur, and as such also helps you to correctly determine the identity and structure of the products.

      Feel free to continue posting your A level Chem qns here all the way till your A levels at the end of the year, Light5! ;)

      Edited by UltimaOnline 01 Aug `15, 7:15AM
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    • Btw Gohby, this thread is getting too long, please start a new thread each time you ask new questions, with the title reflecting the topics involved. This is for efficiency of viewing by members and visitors. Thanks.

      Edited by UltimaOnline 31 Jul `15, 11:17AM
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    • Q7 - Oxides of N have OS of N in the positive OS (since O is more electronegative than N). NH3 has N in the negative OS (since N is more electronegative than H). Hence N is reduced, and when somebody's reduced, somebody's gotta be oxidized. Here, obviously H is being oxidized (since H is a reactant with OS of 0) to H2O.

      Q1. Yes, you're correct. The point referred to is the 1st equivalence point.

      Q2. An ambiguous qn. Don't trust Singapore JC Prelim papers. You can argue the relevancy of 1st statement vis-à-vis the 2nd statement either way. Your thought process is fine, just that the 1st statement rather *indirectly* relates to the 2nd statement. The given answer's option (which you didn't reveal) probably relates more *directly* to the 2nd statement.

      Q3. The Ka of an acid depends on both temperature and solvent. By default, the solvent is always water, unless otherwise specified. Which is why, based on the solvent as water, temperature is thus the only (other) factor that affects the Ka value. Since NH3 is a stronger base than H2O, NH3 is able to deprotonate HA to a greater degree, and hence the Ka value of any acid HA, would be larger in NH3 than in H2O.

      You're welcome to keep your questions coming, Gohby! :Þ

      Edited by UltimaOnline 31 Jul `15, 11:15AM
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    • Q7 - Oxides of N have OS of N in the positive OS (since O is more electronegative than N). NH3 has N in the negative OS (since N is more electronegative than H). Hence N is reduced, and when somebody's reduced, somebody's gotta be oxidized. Here, obviously H is being oxidized (since H is a reactant with OS of 0) to H2O.

      Q1. Yes, you're correct. The point referred to is the 1st equivalence point.

      Q2. An ambiguous qn. Don't trust Singapore JC Prelim papers. You can argue the relevancy of 1st statement vis-à-vis the 2nd statement either way. Your thought process is fine, just that the 1st statement rather *indirectly* relates to the 2nd statement. The given answer's option (which you didn't reveal) probably relates more *directly* to the 2nd statement.

      Q3. The Ka of an acid depends on both temperature and solvent. By default, the solvent is always water, unless otherwise specified. Which is why, based on the solvent as water, temperature is thus the only (other) factor that affects the Ka value. Since NH3 is a stronger base than H2O, NH3 is able to deprotonate HA to a greater degree, and hence the Ka value of any acid HA, would be larger in NH3 than in H2O.

      You're welcome to keep your questions coming, Gohby! :Þ

      Edited by UltimaOnline 31 Jul `15, 11:15AM
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    • Gohby asked :

      Hi UltimaOnline, I have some further questions (on ionic equilibria this time):

       

      Re Q7 @ 21 Jul 15: this is a redox reaction (which more capable students should be able to recognize based on the description given)

       

      Remarks: How can I recognise that it’s a redox reaction? Just because there’s reduction when a nitrogen oxide is reduced to ammonia? But how does that ensure oxidation will occur?

       

      Q1:

       

      http://img.photobucket.com/albums/v700/gohby/Chemistry/CJC2012_zpsnohp6cyi.jpg

       

      Answer: 1 and 2 are correct.

       

      Remarks:

       

      1. For 2, what is meant by the point when the slope of the curve is at maximum at its centre?? Is it the point as indicated by the arrow (which I have inserted) in the diagram? If so then 2 is correct because the first neutralisation reaction would have been complete and the salt produced has no net charge.

      2. For 3, is it wrong because at pH 9.7, there are equal concentrations of H3N+CH(CH3)COO- and H2NCH(CH3)COO- (because pH= pKa → max buffer capacity → where the concentrations of the weak acid and its conjugate base is the same)

       

      Q2: Does this statement “H+ (aq) + OH¯ (aq) ions react exothermically” give a correct explanation for “The ionic product of water, Kw increases with increasing temperature”?

       

      Remarks: I am of the opinion that the first statement gives a correct explanation for the second statement. Given the water dissociation equation: H2O ↔ H+ + OH¯, if H+ (aq) + OH¯ (aq) ions react exothermically, the forward reaction must be endothermic. Hence, when the temperature increases, by LCP, the equilibrium will be shifted to the right to minimise the disturbance, which would increase the concentration of H+ + OH¯ at equilibrium, which will increase the ionic product of water. However, according to the answer, the statement statement “H+ (aq) + OH¯ (aq) ions react exothermically” does not give a correct explanation for “The ionic product of water, Kw increases with increasing temperature” and I don’t understand why.

       

      Q3:

       

      http://img.photobucket.com/albums/v700/gohby/Chemistry/CJC20122_zps4ftdajiy.jpg

       

      Remarks: Why is B wrong? I thought the degree of dissociation, which is related to the Ka, will only be affected by changes in temperature? How is D the correct answer? (Kb of ammonia is larger than water → it is a stronger base than water → what’s the relation of the strength of HA in liquid ammonia?

       

      Thank you for your help, much appreciated. :)

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    • Prime Minister Datuk Seri Najib Razak admitted that US$700 million (RM2.6 billion) was transferred into his accounts, former deputy prime minister Tan Sri Muhyiddin Yassin said in a video (see below) that has leaked on the Internet.

      In the video, Muhyiddin appeared to be informing his guests at his home last night that he had confronted Najib on The Wall Street Journal's report that US$700 million (RM2.67 billion) of funds from 1Malaysia Development Bhd (1MDB)-linked firms were deposited into Najib's personal accounts.

      "I asked him (Najib) from whom? He did not mention the name, from somewhere in the Middle East. How much?... Hard to count, he said 'a lot, a lot'.

      "Then I asked why was it transferred to your accounts?... Why did it enter Najib Razak's accounts? How much money? US$700 million.

      "If you multiply that by three point something...2.6 billion goes into his personal account. He said this, he admitted," Muhyiddin said in the leaked video.

      The video ends abruptly after Muhyiddin says, "so I said why did you put into your personal account".

      In the video, Kedah Menteri Besar Datuk Mukhriz Mahathir could be seen seated beside Muhyiddin.

      Mukhriz's visit to the former deputy prime minister's house took place yesterday, the same day Najib reshuffled the Cabinet, dropping Muhyiddin as his deputy.

      Muhyiddin was sacked two days after he told an Umno Cheras division meeting that The Wall Street Journal's report was a serious matter that needs explaining.

      https://www.youtube.com/watch?v=n8lxLVTaLaM&feature=player_embedded

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    • Looking at the FB comments, lots of selfish WP supporters are demanding all other Opposition parties (including those who have worked the ground hard for years in certain GRCs, while the WP didn't do a thing for these GRCs) to give way to WP just "so as to avoid 3 cornered fights so we can defeat the evil PAP". Have you heard the story of Animal Farm?

      https://www.facebook.com/nspsg/timeline

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