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 Posted: Thu Jul 14, 2005 5:21 pm
I wondering if anyone is in the mood to be my tutor for 100 an hour, I'm also willing to add an aditional 50 gold per person after that.
# Rate each
1 @ 100 gold
2 @ 75 gold
3 @ 65 gold
4 @ 60 gold
The subject is simple, acid and bases. Just need a review and help with pH levels and such. Starting with a quick review of acids, and moving up towards to pH levels. Basic freshman level course with a high stress on the math. Definations are limited so I only need a breifing on the jargon, it will be mostly math.
Acid and Bases:
Arrhenius concept of acids and bases
Bronsted-Lowry model
conjugate acid-bass pairs
Acid Strength:
ideantifying the strong and weak acids/bases
writing equations
Water as an Acid and a Base:
amphoteric substance
ionization of water
ion-product constants
calculating ion concentrations in water
using ion-product constant in calculations
The pH Scale:
Everything
MATH!!
calculating the pH of Strong Acid Solutions
Buffered Solutions
end ^_^;
Also note: If you complete this course I'll pay 500 gold as a minimium ^_^;; So if you do it in 1 hour it's 500 an hour, but it's split between members like before. So let me know who is interested.
Employed:
1)
2)
3)
4)
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Posted: Thu Jul 14, 2005 5:26 pm
I'll help you if you need help, I love acid-base chemistry heart
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Posted: Thu Jul 14, 2005 5:27 pm
Chemical_Kitten I'll help you if you need help, I love acid-base chemistry heart ^_^ ty where do you want to start O-o;
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Posted: Thu Jul 14, 2005 5:28 pm
Amidakun Chemical_Kitten I'll help you if you need help, I love acid-base chemistry heart ^_^ ty where do you want to start O-o; I don't know, where would you like to start? I just woke up xd
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Posted: Thu Jul 14, 2005 5:30 pm
XD I wish I could sleep in x-x I've been staying up to 1-2am every night lately and waking up at 6 x-x;
I guess we can start with where my book starts so i can keep up better
Basicaly it starts with acids and bases and how they work. Basic defination lol
then with the equations
HCL -> H + Cl
and go from there I suppose
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Posted: Thu Jul 14, 2005 5:32 pm
Amidakun XD I wish I could sleep in x-x I've been staying up to 1-2am every night lately and waking up at 6 x-x; I guess we can start with where my book starts so i can keep up better Basicaly it starts with acids and bases and how they work. Basic defination lol then with the equations HCL -> H + Cl and go from there I suppose Hehe, it's only 10:30am here xd So, would you like me to give you a definition of each of the different acid-base concepts?
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Posted: Thu Jul 14, 2005 5:33 pm
Chemical_Kitten Amidakun XD I wish I could sleep in x-x I've been staying up to 1-2am every night lately and waking up at 6 x-x; I guess we can start with where my book starts so i can keep up better Basicaly it starts with acids and bases and how they work. Basic defination lol then with the equations HCL -> H + Cl and go from there I suppose Hehe, it's only 10:30am here xd So, would you like me to give you a definition of each of the different acid-base concepts? Hai, then explain how they work in equations
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Posted: Thu Jul 14, 2005 5:55 pm
Arrhenius concept of acids and bases
Okay... this theory says that an acid is something which contains a hydrogen ion and donates it. This can be seen through this basic equation:
HX + H2O --> H3O+ + X-
To determine the strength of an arrhenius acid/base, it depends on the dissociation constant. So, the extent at which the hydrogen dissociates from the reactant.
Bronsted-Lowry model
This theory is very similar but there is one main difference. Instead of the reactant donating a hydrogen, it is donating a proton. So, this theory is more broad. The acid is the proton donor, and the base is the proton acceptor. This reaction shows hydrogen as the proton:
HCN + H2O --> H3O+ + CN-
The HCN is the acid because it donates a proton and the water is the base because it accepts the proton to become a hydronium ion. Therefore, because this reaction is in equilibrium (I can't draw the double direction arrows on here), the hydronium ion is also an acid and CN- a base. The reaction is moving in both forward and backward because of the equilibrium constant.
Conjugate acid-bass pairs
We'll continue on with the HCN reaction I used in the bronsted-lowry definition. As I said, the hydronium ion also acts as an acid and CN- as a base. So, HCN is the conjugate acid of the base CN-, and H2O is the conjugate base of H3O+. They both work together if you know what I mean. The conjugate acids and conjugate bases work along side each other in equilibrium.
The HCN is the acid and when it donates a proton, it becomes CN-, and so it is the conjugate acid.
The H2O is the base and when it accepts a proton, it becomes H3O+, and so it is the conjugate base.
Just remember, that if you view the reaction from the reverse that the conjugate acid/base terms also switch. H2O is the conjugate base of H3O+, but H3O+ is the conjugate acid of H2O. You can remember this by understanding that the species you say first is the one which determines whether it is a conjugate acid or conjugate base. so, if H3O+ is the conjugate acid of H2O, H3O+ must be an acid, which it is because it donates a proton to become H2O.
I hope this makes sense... sorry I took so long, trying to make breakie xd
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Posted: Thu Jul 14, 2005 6:28 pm
Alright let me review:
The Arrhenius concept of acids and bases is that a compound must donate a hydrogen ion to be considered a base.
The Bronsted-Lowry model is that instead of donating hydrogen ions, protons are donated instead. This creates a balance equation in which the reaction can occur backwards and fowards. Thus, conjugate acid-base pairs are formed.
Notes:
Acids donate a proton.
Bases recieve a proton.
With the equation:
HCN + H2O --> H3O+ + CN-
the following can be determined...
HCN + H2O --> H3O+ + CN-
Acid
Base
Conjugate Acid
Conjugate Base
if the reactions are reversed we can derive...
H3O+ is the conjugate base of H2O because H2O recieves a proton from HCN and becomes H3O+.
I believe this is correct... x-x;
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Posted: Thu Jul 14, 2005 6:42 pm
Amidakun Alright let me review: The Arrhenius concept of acids and bases is that a compound must donate a hydrogen ion to be considered a base. The Bronsted-Lowry model is that instead of donating hydrogen ions, protons are donated instead. This creates a balance equation in which the reaction can occur backwards and fowards. Thus, conjugate acid-base pairs are formed. Notes: Acids donate a proton. Bases recieve a proton. With the equation: HCN + H2O --> H3O+ + CN- the following can be determined... HCN + H2O --> H3O+ + CN-AcidBaseConjugate AcidConjugate Baseif the reactions are reversed we can derive... H3O+ is the conjugate base of H2O because H2O recieves a proton from HCN and becomes H3O+. I believe this is correct... x-x; I think an easier way to see the difference is that an Arrhenius acid donates hydrogen but a bronsted-lowry acid donates protons. So, a bronsted-lowry definition is more broad and can be used in metal chemistry even to lable compounds as acids or bases. Li+ can act as a proton to make the reacting compound an acid. Arrhenius definition would not consider it an acid though, because it is not a hydrogen ion. With your equation, you got the acid and base labelling correct, but the conjugate pairs need to be defined as to what way you are labelling them. Are you reading the equation from the left or from the right? When you explained in the last paragraph, it's wrong... sweatdrop H3O+ is the conjugate acid of H2O because H3O+ donates a proton. H2O is the conjugate base of H3O+ because H2O accepts a proton. HCN is the conjugate acid of CN- because HCN donates a proton. CN- is the conjugate base of HCN because CN- accepts a proton. It makes it easier if you consider these as seperate reactions. So, in your mind, consider H3O+/H2O as one reaction and HCN/CN- as another reaction. It makes it easier to keep them seperate and to distinguish the conjugate acid/bases. Does this make sense?
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Posted: Thu Jul 14, 2005 6:50 pm
Alright so in summary:
The conjugate is the source, because H3O+ donates a proton, and acids are defined as donating a proton.
So that means that...
H2O is the conjugate base because it accepts a proton.
H3O is a conjugate acid because it donates a proton.
In general when in doubt the one with the most protons is most likely the acid and the one with the least is the base. ^_^; correct?
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Posted: Thu Jul 14, 2005 6:59 pm
Amidakun Alright so in summary: The conjugate is the source, because H3O+ donates a proton, and acids are defined as donating a proton. So that means that... H2O is the conjugate base because it accepts a proton. H3O is a conjugate acid because it donates a proton. In general when in doubt the one with the most protons is most likely the acid and the one with the least is the base. ^_^; correct? Yeah, that's right smile I guess you could think of it that way... just look at the conjugate pairs and work it out that way smile
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Posted: Thu Jul 14, 2005 7:02 pm
lol ok.. well anyway I guess the next thing is weak and strong acids, but I only need a brief idea of it. I understand most of it.
I'm confused on how to tell the diffrence between a weak and strong acid though.. I belive it's related to the pH scale. x-x;
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Posted: Thu Jul 14, 2005 7:30 pm
Amidakun lol ok.. well anyway I guess the next thing is weak and strong acids, but I only need a brief idea of it. I understand most of it. I'm confused on how to tell the diffrence between a weak and strong acid though.. I belive it's related to the pH scale. x-x; Okay... strong and weak acids... Whether something is a strong or weak acid depends on the dissociation of the proton. If the proton dissociates from the acid easily and to a higher amount, then the acid is strong. If it doesn't, then it is weak. Some of these you should know off by heart. Organic acids tend to be weak whereas the metal acids tend to be stronger. With bases, most ionic hydroxides are strong bases such as NaOH and KOH. Um... also in a question, you could be given the Ka or Kb values. This is basically a value given to the dissociation. The larger the Ka, the stronger the acid. Therefore, the more ions that are present ta equilibrium is relative to the unionised molecules. A Ka larger than 1 means that it is a strong acid. This means that the acid is completely ionised in solution. Kb is basically the same, but it relates to the base instead. You can work out each of these values by knowing the other one and Kw (water). Ka + Kb = Kw. Eg. 10^-4 + Kb = 10^-14 Kb = 9.9999x10^-5 The Ka or Kb value can be used to solve for pH. pH = -log[H3O+] I'll do an example to make it easier to understand. 0.3M acetic acid Ka = 1.8 x 10^-5 spaaaaaaaaaaaaaaaaaaaaaaaaaaceHC2H3O2 --> H3O+ + C2H3O2- Initial concentration: spaaaaaaaaaaaace0.3M spaaaace0 spaaaace0 Equilibrium concentration: spaaaaace0.3 - xM spaaacexM spaaacexM note: square brackets indicate concentration Ka = [products]/[reactants] 1.8 x 10^-5 = Ka = (x^2)/(0.3-x) = (0.3) x = 2.3x10^-3 pH = -log[H3O+] pH = -log(2.3x10^-3) pH = 2.6 I hope that answers your question sweatdrop
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Posted: Thu Jul 14, 2005 7:36 pm
I'll give you a table I have on common strong acids and bases:
Strong acids
HCl (hydrochloric)
HBr (hydrobromic)
HI (hydroiodic)
HCIO3 (chloric)
HCIO4(perchloric)
HNO3 (nitric)
H2SO4 (sulphuric)
Strong bases
Group 1A metal hydroxides (LiOH, NaOH, KOH, RbOH, CsOH)
Heavy group 2A metal hydroxides (Ca(OH)2, Sr(OH)2, Ba(OH)2)
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