What is K? (A Mind-Map Style Explanation)

As I had mentioned in the introductary post to this blog, I had a real hard time figuring out what "K" meant until it was finally revealed to me. Even then, I pretty much didn't have the right answer until I took the professor's advice and made a flowchart of what "K" actually is. Here below is a hand-drawn mind-map of K, and represents much of what we learned in Chem II. I apologize in advance for the sloppy penmanship. Part of the assignment required that I write it by hand, rather than make the chart on computer.

Click on image for the Large Version

As you can see, K, as it applies to most of second semester inorganic chemistry, is a thermodynamic constant, and is largely the distilled essence of everything from solubility to electrochemistry, and most points in-between. Despite the fact we were, throughout the semester, educated on the values of Kc, Ka, Ksp, and many other constants, they all are simply different aspects of K. The value in learning this is in finding out exactly how a constant comes into being. I'm sure most of you by now have encountered the Ideal Gas Constant, or Faraday's Constant, Coulomb's Constant. or even Avogadro's Number, and wondered "that's great, and all, very useful stuff to know, but how do these constants come about in the first place?"

Unlike the ones I mentioned, K is a dynamic constant, in that it is not a number that will always be the same. It changes depending on the values fed to it, but the formula, the product of the concentration of right-hand side of the equation, divided by the product of concentrations of the left-hand side of the equation, helps us to understand where constants come from. In these instances, we are developing our own constants each time. It is through this process we begin to unlock the methodology that the giants before us used to establish the static constants (the numbers that are always the same) by applying very much the same principles, using slightly more advanced math, and many, many trials.

This concept was at first so frustrating for me, and later so inspirational, that it resulted in the creation of this blog, and hence, the name, The Daily Constant. It helps us each to remember that it is you who hold the future of scientific breakthroughs in your hand, not those who came before you. They hold the past, but it is up to you to come up with the constants others will use for ages to come, and to unlock the knowledge and additional mysteries it brings.

Chem II: Final Exam Review (Part 4/4)

(quick links to all 4 parts)


Ch. 12 and 13 Practice Test (Solutions and Rates of Reaction) 

Chapter 14-16 Practice Test (Part 2: Chemical Equilibrium, Acids and Bases, and Acid-Base Equilibria)

Chapter 17 and 18 Practice Test (Part 3: Solubility and Complex-Ion Equilibria, and Thermodynamics and Equilibrium)

Chapters 19, 20, and 23 Practice Test (Part 4: Electrochemistry, Nuclear Chemistry, and Organic Chemistry)

Chapters 19, 20, and 23 Practice Test

(Part 4: Electrochemistry, Nuclear Chemistry, and Organic Chemistry)

Nuclear Chemistry

1.       What is the A,X,Z of an atom? A = Mass Number, X = Element, Z = Protons (Atomic #)

2.       What are the 5 types of spontaneous radioactive decay?

Name & Sym	Particle	Formula	Z#	A#	Reason
Alpha α	42He	-	-2	-4	Z > 83
Beta β-	0-1e	10n --> 11p + 0-1e	+1	0	N/Z too large
Positron β+	0+1e	11p --> 10n + 0+1e	-1	0	N/Z too small
Electron Cap. (EC)	X rays	11p + 0-1e --> 10n	-1	0	N/Z too small
Gamma  γ	00 γ	-	0	0	Excited

3.       What is the highest non-radioactive atomic number?      - 83

4.       What are the magic numbers of stability?

a.       For Protons?      2, 8, 20 , 28, 50, 82

b.      For Neutrons?   2, 8, 20, 28, 50, 82, 126 (maybe 114)

c.       What is the general guideline for stability?           - Even #’s more stable than odd #’s.

5.       What is a Curie (definition and constant)? Nuclear disintegrations per unit time occurring in a radioactive material.  Ci = 3.7 x 10¹⁰

6.       What is the formula for finding Half-Life?              T_1/2 = 0.693

k

7.       What is the formula for finding the Rate of Decay?           Rate = kN_t

Organic Chemistry

1.       What are the three basic types of Hydrocarbons?

a.       How reactive are they?

b.      What types of reactions are they typically capable of?

Saturated	Not very reactive	Combustion w/Oxy or Halo
Unsaturated	Very reactive	Addition Reaction, Combustion
Aromatic	Not very reactive	Replacement Reactions

2.       What are the families of each of the three basic types of Hydrocarbons?

a.       What group(s) of carbon families does each include?

b.      What type of electron bond(s) exists for each family?

c.       What is the general formula for each family?

Saturated	Alkanes	C-C chains	CnH(2n+2)
Saturated	Cycloalkanes	C-C rings	CnH(2n)
Unsaturated	Alkene	C=C chain	CnH(2n)
Unsaturated	Alkyne	C≡C chain	CnH(2n-2)
Aromatic	Benzene	C-C/C=C rings	C6H6

3.       What are the first ten alkanes?

a.       CH4        methane

b.      C2H6      ethane

c.       C3H8      propane

d.      C4H10   butane

e.      C5H12   pentane

f.        C6H14   hexane

g.       C7H16   heptane

h.      C8H18   octane

i.         C9H20   nonane

j.        C10H22 decane

4.       What are the first four alcohols and their chemical formulas?

a.       CH3OH                                  Methanol

b.      CH3CH2OH                          Ethanol

c.       CH3CH2CH2OH                  Propanol

d.      CH3CH2CH2CH2OH          Butanol

5.       What is the difference between a primary, secondary, and tertiary alcohol?

a.       Primary has one Carbon group attached to the carbon attached to the OH group.

                                                               i.      eg.   C-C-C-OH

b.      Secondary has two Carbon groups attached to the carbon attached to the OH group.

c.       Tertiary has three.

6.       Name the following compounds:

7.       What is an Aldehyde (and its suffix)? Suffix = “al”

a.       What is its R-group positioning?

b.      What is its molecular tail?             -CHO

c.       Draw Formaldehyde (methanal)

8.       What is a Ketone (and its suffix)? Suffix = “one”

a.       What is its R-group positioning?

 

b.      What is its molecular tail?  =O

c.       Draw acetone (propone)

9.       What would happen if litmus paper were dipped into an Amine?

a.       It would turn red litmus paper blue.

_{the end}

Chem II: Final Exam Review (Part 3/4)

(quick links to all 4 parts)


Ch. 12 and 13 Practice Test (Solutions and Rates of Reaction) 

Chapter 14-16 Practice Test (Part 2: Chemical Equilibrium, Acids and Bases, and Acid-Base Equilibria)

Chapter 17 and 18 Practice Test (Part 3: Solubility and Complex-Ion Equilibria, and Thermodynamics and Equilibrium)

Chapters 19, 20, and 23 Practice Test (Part 4: Electrochemistry, Nuclear Chemistry, and Organic Chemistry)

Chapter 17 and 18 Practice Test

(Part 3: Solubility and Complex-Ion Equilibria,

and Thermodynamics and Equilibrium) 

1.       Write the Ksp expression and x-formula for the following salts:

a.       Ca(OH)₂

                                                               i.      K_sp = [Ca²⁺][OH^-]²

                                                             ii.      K_sp = (x) * [(2x)²]

b.      Na₃PO₄

                                                               i.      K_sp = [Na⁺]³[PO₄^3-]

                                                             ii.      K_sp = [(3x)³][x]

2.       What are Ksp and Qsp, and what is the difference between them?

a.       Ksp = Product Solubility Constant, it tells you the solubility of a salt in water at equilibrium. It may be used to tell if a precipitate will form upon at equilibrium.

b.      Qsp = Reaction Quotient, Ratio of Products over reactants at instant of mixing. Can also be expressed as Qip to determine if a precipitate will form upon the instant of mixing.

c.       If Qip > Ksp, then the solution is super-saturated (precipitate forms)

d.      If Qip = Ksp, then the solution is saturated and at equilibrium.

e.      If Qip < Ksp, then it is unsaturated, and there is no precipitate.

3.       45mL of 0.015M CaCl₂ is added to 55mL of 0.010 M Na₂SO₄.

a.       What is the Qip?

                                                               i.      3.71 x 10^-5

b.      What is the Ksp?

                                                               i.      2.4 x 10^-5

c.       Will a precipitate form, and why or why not?

                                                               i.      Qip > Ksp, so a Precipitate will form.

4.       The solubility of magnesium oxalate, MgC₂O₄ in water is 0.0093 mol/L. Calculate K_sp

a.       8.65 x 10^-5

5.       The solubility of silver chromate, Ag₂CrO₄ in water is 0.022 10⁰ g/L. Calculate K_sp.

a.       1.16 x 10^-12

6.       What is a complex ion, how are the formation and dissociation constants for it expressed? Give an acidic and basic example.

a.       A complex ion is an anion that is composed of a metal and one or more ligands.

b.      A ligand is a molecule or anion bound to a metal through coordination of lone pairs.

c.       The Formation Constant is Kf and the Dissociation constant Kd = 1/Kf.

d.      Typically the Kf for a complex ion is very large and the reaction goes to completion.

e.      Co(H₂O)₆²⁺ - CoCl₄^2- are both examples of a complex ion (Co) bound to ligands.

f.        The complex ion acts as a Lewis Acid, accepting elections.

g.       The ligands act as a Lewis Base, donating elections.

h.      Solubility is increased because the formation of it removes a product.

7.       The solubility of magnesium fluoride, MgF₂, in water is 0.016 g/L. What is the solubility (in grams per liter) of magnesium fluoride in 0.014 M sodium fluoride, NaF?

a.       2.2 x 10^-5 g/L

8.       What is the solubility of MgF₂ in water? The K_sp for MgF₂ is 7.4 x 10^-11

a.       2.6 x 10^-4 M

9.       What are the Thermodynamic State Functions?

a.       E, G, S, P, T, H, V, Qp “Every Good Student Picks The Hot Valentine Qp.”

10.   Which Thermodynamic variables are not State Functions?

a.       q (heat) and w (work).

11.   Why study Thermodynamics?

a.       It can tell us if a reaction is possible, the entropy, energy, and whether or not it is spontaneous or not. This saves us time, energy, money, and frustration.

12.   Why study Kinetics?

a.       It can tell us how fast a reaction happens, how we got there, the reaction mechanism, and collision theory.

13.   What is ∆H, and what can it tell us, and how?

a.       Enthalpy, also known as q_p, and is a state function.

b.      If ∆H is negative, heat is a product and the reaction is exothermic.

c.       If ∆H is positive, heat is a reactant, and the reaction is endothermic.

14.   Are the following situations more likely to be Spontaneous or NonSpontaneous?

a.       Flow of heat from a hot place to a cold place?                     (Spontaneous)

b.      State change from liquid to solid?                                             (Non-Spontaneous)

15.   What is Gibb’s Free Energy Equation and what must be remembered?

a.       ∆G = ∆H - T∆S

b.      Remember ∆S is in Joules, not KiloJoules.

c.       ∆G = 0 at equilibrium.

16.   How can Gibb’s Equation be used to determine K , and what must be remembered?

a.       ∆G = -RT ln(K)

b.      Ln(K) = ∆G / -RT

c.       Convert ∆G to Joules, as R is our constant.

d.      ∆G = 0 at equilibrium.

17.   What are the units of measurement in the following?

a.       ∆G = kJ/mol

b.      ∆S = J/K

c.       ∆H = kJ/mol

d.      R = J/K*mol

18.   What is the 1^st Law of Thermodynamics and its associated formula?

a.       Energy can neither be created nor destroyed.

b.      Change in Internal Energy (∆u) is equal to the heat of the reaction plus the work done to the system.

c.       ∆u = q+w        (Internal Energy = Thermal + Kinetic Energy.)

19.   What is the 2^nd Law of Thermodynamics and its associated formula?

a.       Entropy will increase if a process is spontaneous.

b.      ∆S > (q/T) is a spontaneous reaction

c.       ∆S = (q/T) is an equilibrium reaction

d.      ∆S < (q/T) is a non-spontaneous reaction

20.   What is the 3^rd Law of Thermodynamics and its associated formula?

a.       Entropy will increase with temperature.

b.      The Entropy of a perfectly ordered crystalline substance at 0 K is 0.

21.   Which anions are soluble in acidic solutions? Why? Give examples.

a.       Very Basic Anions will be more soluble in acid than water.

b.      F-, CO₃^2-, S^2-, OH^-, PO+4^3-

c.       Weak Basic Anions will not be affected much by pH.

2.       Under what conditions do the following indicate a spontaneous reaction?

a.       K ?          (If value is greater than 1.0 x 10³ it is spontaneous and favors products)

b.      ∆G          (if value is negative)

c.       ∆S           (if value is positive)