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9 Cards in this Set
- Front
- Back
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What is the Lowry-Bronsted theory of acids and bases in aqueous solutions?
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An acid is defined as a proton donor and a base is a proton accepter.
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Describe and give an example of a conjugate pair.
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A conjugate pair is an acid on one side of an equilibrium and a chemically similar base on the other side. e.g HCl + H2O <-> H3O+ + Cl- The HCl and Cl- are 1 conjugate pair and the H2O and H3O+ are the other.
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What is the definition of pH?
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pH= -log10[H+]
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What calculator buttons would you press to find the [H+] from the pH?
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[shift][log][-][pH]
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What is the difference between a strong acid and a concentrated acid?
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A strong acid is an acid that completely dissociates into it's ions whereas a concentrated acid just means there is lot of solute dissolved in the solution.
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What is the Kc expression for the ionic product of water?
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Kc=[H+][OH-]/[H2O]=1.8x10-16
This is at 298K |
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How would you calculate the Kw of water and subsequently the pH of water?
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Because water only ionises slightly we assume that [H2O] is a constant. So to 'tidy up' we combine both the constants to get Kw. Kc=[H+][OH-]/[H2O] goes to Kc x [H2O] = [H+][OH-]. Kc of water is 1.8x10-16 and the conc. of pure water is the same as the Mr so 55.56.
So, if we put in the numbers 1.8x10-16 x 55.56 = 1x10-14. Kw=1x10-14=[H+][OH-] because H+ and OH- are in a 1:1 ratio to find [H+] we just square root Kw which is 1x10-7 and from there pH=-log10(1x10-7) = 7. |
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At 313K Kw is 2.9x10-14 and the pH of water is 6.76 is water still neutral?
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Yes because although this means that there are more H+ ions there are also more OH- ions so they neutralize each other.
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Calculate the pH of 2M H2SO4.
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H2SO4 is a strong acid so it dissociates completely H2SO4 -> 2H+ + SO4-. So the conc. of each ion is the same as the conc. of the whole molecule, each is at 2M, but because there is 2 lots of H+ we have to double 2 to get 4 and then this goes into the pH equation. pH=-log10(4) to get a pH of -0.6
(minus pH's do exist don't panic if one appears) |
