Chemistry: 5A: Acids, Bases, and Buffers
Kw is the Auto-ionization constant or Ion product constant Kw=[H3O+][OH-]
*Khan Academy: Auto-ionization of water: https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/v/autoionization-of-water*
Kw=[H3O+][OH-]=[1.0 x 10^-7] [1.0 x 10^-7]= 1.0 x 10 ^-14
*Khan Academy: Auto-ionization of water: https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/v/autoionization-of-water*
When [H3O+] = [OH-] the solution is said to be neutral When [H3O+] > [OH-] the solution is said to be acidic When [H3O+] < [OH-] the solution is said to be basic
*Khan Academy: Auto-ionization of water: https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/v/autoionization-of-water*
What equation can we use to solve for the pH of a buffer solution?
*Khan Academy: Buffer Solutions: https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/v/buffer-solutions*
In terms of a conjugate acid base pair Ka x Kb = Kw For example: HCl/ Cl^- The Ka of HCl x Kb of Cl^-= Kw
*Khan Academy: Relationship between Ka and Kb: https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/v/relationship-between-ka-and-kb*
For a Strong Acid [H3O+] is equal to the molar concentration of the *Strong Acid*, and [OH-] is equal to the molar concentration of the *Strong Base*
*Khan Academy: Strong Acids and Strong bases: https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/v/strong-acids-and-strong-bases*
Name the 7 strong acids
*MCAT Self Prep: Acids and Bases deck*
The equation of pH is
*https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/a/chemistry-of-buffers-and-buffers-in-blood*
The equilibrium constant of an acid is:
*https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/a/chemistry-of-buffers-and-buffers-in-blood*
Increasing acid strength trend
*https://www.shmoop.com/acids-bases/acid-strength.html*
What is the difference between a Bronsted Lowry base and its conjugate acid and a Bronsted Lowry acid and its conjugate base?
1 H+ atom *Khan Academy: Acid base definitions: https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/v/acid-base-definitions-1*
What does it mean to be amphoteric?
A molecule can act as an acid or base Like water *Khan Academy: Auto-ionization of water: https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/v/autoionization-of-water*
Arrhenius acids are compounds that produce _______ in water. A. H+ B. OH- C.NaOH D. salts
A. H+ Arrhenius acids are compounds that produce H+ in water. *Arrhenus, Bronsted Lowry and Lewis Acids and Bases: https://www.youtube.com/watch?list=PLdonEKZrk3DmPSpqpqHua-jQkZLmEGWbL&time_continue=109&v=ELpqyBoLZ4c*
A Lewis acid is an electron __________, and a Lewis Base is an electron ___________. A. acceptor, donor B. donor, acceptor C. acceptor, acceptor D. donor, donor
A. acceptor, donor Think Lewis *A*cid, *a*cceptor Think Lewis *B*ase, *d*onor (if you flip the d it becomes a b) *Khan Academy: Acid base definitions: https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/v/acid-base-definitions-1*
If Ka >>1 the acid is ________, if Ka <<1 the acid is ________. A. strong, weak B. weak, strong C. neutral, strong D. weak, neutral
A. strong, weak If Ka>>1 = Strong acid Ka<< 1 = Weak acid *Khan Academy: Ka and acid strength: https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/v/ka-and-acid-strength*
What is the other way of preparing a buffer?
A. using a Phosphate buffer which is made up of a weak base HPO4^2- and H2PO4^- the pH of a phosphate buffer is usually maintained at a physiological pH of 7.4 *https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/a/chemistry-of-buffers-and-buffers-in-blood*
pka is equal to A. - log (pH) B. - log (Ka) C. - log (Kb) D. - log (pOH)
B. - log (Ka) pKa= - log(Ka) *Khan Academy: Weak Acid Equilibrium: https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/v/weak-acid-equilibrium*
Arrhenius bases are compounds that produce _______ in water. A. H+ B. OH- C.NaOH D. salts
B. OH- Arrhenius bases are compounds that produce OH- in water. *Arrhenus, Bronsted Lowry and Lewis Acids and Bases: https://www.youtube.com/watch?list=PLdonEKZrk3DmPSpqpqHua-jQkZLmEGWbL&time_continue=109&v=ELpqyBoLZ4c*
A Brownstead Lowry Acid is a proton __________, and a Bronstead Lowry Base is a proton ___________. A. acceptor, donor B. donor, acceptor C. acceptor, acceptor D. donor, donor
B. donor, acceptor *Khan Academy: Acid base definitions: https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/v/acid-base-definitions-1*
Based on Le Chatlier's principles: If you increase the concentration of one of your products you shift the reaction to the __________. A. left, toward the products B. left, towards the reactants C. right, towards the products D. right, towards the reactants
B. left, towards the reactants *Khan Academy: Common Ion Effect and buffers: https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/v/common-ion-effect*
If Ka ( > 1) is high that means we have a ____________ acid. A. weak B. strong C. neutral D. Lewis
B. strong, it means we have a strong acid because our reaction will favor our products and we will have more products than reactants making us have a large Ka Ka= [H3O+][Cl-]/ [HCl] *Khan Academy: Ka and acid strength: https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/v/ka-and-acid-strength*
The smaller the pKa value the _________ the acid A. weaker B. stronger
B. stronger, The smaller the pKA value the stronger the acid , the same goes for pKb, the smaller the pkB the stronger the base *Khan Academy: Weak Base Equilibrium: https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/v/weak-base-equilibrium*
The ________ the acid, the ________ the conjugate base. A. stronger, stronger B. weaker, weaker C. stronger, weaker D. weaker, stronger
C. The stronger the acid, the weaker the conjugate base. *Khan Academy: Ka and acid strength: https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/v/ka-and-acid-strength*
A buffer has its maximum buffering capacity when its pH is __________ than/to its pKa A. greater B. less C. equal
C. equal *MCAT Self Prep Qs: Buffers*
What is pH dependent on? A. the concentration of OH ions B. the number H+ ions C. the concentration of H+ ions D. the number of OH ions
C. the concentration of H+ ions *https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/a/chemistry-of-buffers-and-buffers-in-blood*
Buffers are prepared by mixing: I. a large volume of a weak acid and its conjugate base (ie acetic acid-acetate ion, CH3COOH and CH3COO^-) II. a large volume of a weak base and its conjugate acid (ie ammonia-ammonium ion, NH3 and NH4+) III. a strong acid and it conjugate base (ie hydrochloric acid and chloride ion, HCl- Cl^-) A. I only B. II only C. I and III only D. I and II only
D. I and II only *https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/a/chemistry-of-buffers-and-buffers-in-blood*
The common ion effect generally _________ solubility of a solute and can effect buffering solutions, as adding more conjugate ions may shift the _____ of the solution. A. decrease, reaction B. Increase, pH C. increase, reaction D. decease, pH
D. decease, pH The common ion effect generally decrease solubility of a solute and can effect buffering solutions, as adding more conjugate ions may shift the pH of the solution. *Khan Academy: Common Ion Effect and buffers: https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/v/common-ion-effect*
What happens if our blood pH goes below 6.8 or above 7.8 (pH of blood is maintained at about 7.4) ?
Enzymes which are very specific in nature and function optimally at the right temperature and pH will stop working and could possibly become permanently denatured. *https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/a/chemistry-of-buffers-and-buffers-in-blood*
In Experiment 1: The pH of solution A is 7.0 i.e. it's neutral. When we add 10 mL of 0.2M HCl to it, the pH decreases to 1.5. On the other hand, when we add 10 mL of 0.2M NaOH to solution A the pH shoots up to 12.5. In Experiment 2: Solution B's pH is maintained at 7.0. When we add 10 mL of 0.2M HCl to it, the pH decreases by only 0.2 units to 6.8. Next, when we add 10 mL of NaOH to solution B, the pH just slightly rises to 7.2 from 7.0. What would you say about Solution B vs. Solution A?
Solution B is definitely a buffer, which is an aqueous solution that resists changes in pH upon the addition of an acid or base *https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/a/chemistry-of-buffers-and-buffers-in-blood*
What happens when you add acid to a buffer HA -> H + A-
The acid will associate with the conjugate base ions and make acid *Khan Academy: Buffer Solutions: https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/v/buffer-solutions*
What happens when you add base to a buffer? HA -> H + A- *Khan Academy: Buffer Solutions: https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/v/buffer-solutions*
Water will be made and more conjugate base (A-) will be added *Khan Academy: Buffer Solutions: https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/v/buffer-solutions*
Calculate the pH of a 0.030 M HNO3 solution. HNO3 +H2O -> H3O + NO3^-
When you are dealing with *Strong* acids the pH is equal to the molar concentration of the acid because it dissociates 100% In this case pH=- log (0.030 )= 1.5 *Khan Academy: Strong Acids and Strong bases: https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/v/strong-acids-and-strong-bases*
What does Ka describe?
acid ionization constant or acid dissociation constant *Khan Academy: Ka and acid strength: https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/v/ka-and-acid-strength*
A strong acid and a weak base will react to form a(n) _________ solution.
acidic, pH will be lower
A weak acid and a strong base will react to form a(n) _________ solution
basic, pH will be higher
A strong acid and a strong base gives you a _________ solution.
neutral, pH=7 its an example of an acid base neutralization reaction bc the reaction forms a salt and water
pKa + pKb = ?
pKw = 14.00 *Khan Academy: Relationship between Ka and Kb: https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/v/relationship-between-ka-and-kb*
What happens when any acidic substance enters the bloodstream?
the bicarbonate ions neutralize the hydronium ions forming carbonic acid and water. Carbonic acid is already a component of the blood buffering system, since hydronium ions are removed this prevents the blood pH from becoming too acidic. *https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/a/chemistry-of-buffers-and-buffers-in-blood*
What is the common ion effect on equilibrium?
the common ion effect occurs when an ion (that is already contained in the solution) is added to a solution. *Khan Academy: Common Ion Effect and buffers: https://www.khanacademy.org/test-prep/mcat/chemical-processes/acid-base-equilibria/v/common-ion-effect*
