GenChem 2 Finale Review
List the following in order of increasing pH assuming a 0.1 M aqueous solution for each:KOH, NH3, HCl, NH4Cl, KI
(lowest pH) HCl < NH4Cl < KI < NH3 < KOH (highest pH)
Types of packing: list and give coordination numbers
- Closest packing (cubic and hexagonal)= 12 -Simple cubic= 6 -Body-centered cubic= 8
weak acid-strong base titration calculation
- when solution contains comparable M of both members prior to equivalence point, its a buffer problem using hesselbalch - if solution contains excess titrant (either strong acid or base) its a pH problem requiring only M
A+B->C+D Rate law= k[B]^2 What is the order with respect to A and B? What is the overall order? What is a plausible mechanism for he reaction
0 and 2 2 Sep 1: B+B-> C+E (slow) Step 2: E+A-> D+B (fast)
1 J (joule E)=
1 C x 1 V 1 joule of work is performed when 1C of charge moves through a potential difference of 1V
2 ways to make a buffer solution
1) equal amounts WA and salt containing conjugate 2) 1 mol weak + 0.5 mol strong
perdict G based on S and H: 1. -H +S -> 2. +H -S -> 3. -H -S -> 4. +H +S ->
1. -G= always spon. 2. +G = always non. 3. -G when TS < H= spon. +G when TS> H = non. 4. -G when TS> H spon. +G when TS< H non.
Consider a galvanic cell that used the reaction: 2 Ag+(aq) + Sn(s) 2 Ag(s) + Sn2+(aq). 1. Write the shorthand notation for this cell 2. Calculate the potential at 25°C for the cell given: [Ag+] = 0.010 M, [Sn2+] = 0.020 M. 3. Calculate ∆G for this cell
1. 0.94v 2. 0.87v 3. -181 kJ
The density of a 16.0 mass% solution of sulfuric acid in water is 1.1094 g/mL at 25.0 C. What is the molarity of the solution?
1. 16g H2SO4/ 100g solution 2. 16g H2SO4 / 98.09 (molar mass) = 0.163 mol 3. 100g solution (1mL/ 1.1094g)(1L/ 1000mL)= 0.0901 L 4. M= 0.163mol/ 0.0901L= 1.81M
Consider the titration of 100.0 mL of 0.06 M HOCl (Ka = 3.5 x 10-8) with 0.0400 M NaOH. How many milliliters of 0.0400 M NaOH are required to reach the equivalence point? Calculate the pH: 1. After addition of 10.0 mL of 0.0400 M NaOH (answer) 2. Halfway to the equivalence point 3. At the equivalence point.
1. 6.31
PART 1: An astronomer uses a lead-acid battery to power his telescope's mount (which tracks the rotation of the earth) while taking a series of star pictures in a remote location. A full night's work requires 10 h of battery power. To minimize the weight he has to carry, he decides to switch to a smaller motorcycle battery, which contains 0.1 L of 5.0 M H2SO4. The setup requires 0.5 A to run.The balanced overall reaction inside the battery is:Pb(s) + PbO2(s) + 2 H2SO4(aq) → 2 PbSO4(s) + 2 H2O(l)a) Write the two half reactions that make up the overall reaction! (3 points each) PART 2: If the battery can run the setup until all H2SO4 has been used up, how many hours of use at 0.5 A does it provide (1+1+4 points)? Fill in the following conversions on the way to the solution:What is the number of electrons transferred in both half reactions (1 point)?How many H2SO4 are used up per Pb atom oxidized during the overall reaction (1 point)?How many hours battery last?
1. Anode: Pb(s) + H2SO4(aq) → PbSO4(s) + 2 H+(aq)_+ 2 e-_(or HSO4- and 1 less H+) 2. Cathode: PbO2(s) + H2SO4(aq) + 2 H+(aq) + 2 e- → PbSO4(s) + 2 H2O(l) Part 2: 2 for both 3. Limiting reagent: H2SO4 0.1 L of 5.0 M: 0.5 mol H2SO4 4. 0.5 mol H2SO4 react with 0.25 mol Pb, producing 0.5 mol e- 5a. I = nel·F/t 5b. I = 0.5 A 6. nel = 0.5 mol 7. F = 96,500 C/mol 8. t = nelF/I = 96,500 s·1 h/3,600 s = 26.8 h
On exam 2, your friend accidentally lowered the pH of your fish tank to 4.75 by adding NH4Cl. You need to take quick action to raise the pH to 6.00 by adding NaOH to rescue the fishes. How much NaOH do you need to add? Follow the steps below!⦁Write the neutralization reaction that is occurring (leave out spectator ions)!⦁Calculate the ratio of [NH3]/[NH4+] that will give a pH of 6.00. HINT: You are creating a buffer system during the reaction in a)! Ka(NH4+) = 5.6 × 10-10⦁Assuming no change in volume, and no other species affecting the pH, calculate the mass of NaOH that you need to add to the 15 L fish tank of 0.56 M NH4Cl to achieve a pH of 6.00!
1. NH4+(aq) + OH-(aq) <-> NH3(aq) + H2O(l) 2. pH = pKa + log[base]/[acid] -> 6.00 = -log(5.6 × 10-10) + log[NH3]/[NH4+] -> log[NH3]/[NH4+] = -3.25 -> [NH3]/[NH4+] = 10-3.25 = 5.6 × 10-4 3. 15 L pf 0.56 M NH4+ contains 8.4 mol NH4+. -> Need: 5.6 × 10-4 · 8.4 mol NaOH. 4.704 × 10-3 mol NaOH needed -> MW(NaOH) = 40 g/mol -> m = n·MW = 0.19 g
steps for determining in reaction is spontaneous by finding its Ssys and Ssurr
1. Srxn is found in table (Ssys) 2. Hrxn also found in table (Hsys) 3. Ssurr= -Hsys/T 4. Suniv= Ssys+ Ssurr
spontaneity is favored by
1. an increase in entropy 2. being exothermic
how to determine effect of pH on solubility
1. determine s 2. then calc pH or pOH depending on substance if substance is placed in a solution with pH less than (or more if acidic) its calculated pH then solubility would increase
steps to calc molar solubility
1. make equilibrium table 2. determine what is known and what is not 3. molar concentrations for compounds can be replaced by s (example-> [Cu2+][OH-]^2 is s(2s)^2 or 4s^3 4. solve for s 5. divide s by liters and multiply by compounds molar mass
relationship btw K and ΔG0: give what is favored in reaction 1. K> 1, lnK is positive, -G0 2. K=1, lnK=0, G0=0 3. K<1, lnK is neg., +G0
1. products 2. neither 3. Reactants
what causes entropy to increase?
1. transitioning from solid to liquid, liquid to gas, and solid to gas 2. dissolving 3. increase temp 4. increase net mole gas 5. in many cases increase in molecule/ions
ΔG0 equation (standard free E)
1. ΔG0= -RT lnK the larger the K is the more neg. G is 2. ΔG0= -RT lnKsp 3. ΔG0= -RT lnKp
second order
1/[A]t = kt + 1/[A]0 rate is proportional to the square of the concentration t1/2 = 1 / k[A]0 M^-1s^-1
Diluting a weak acid by factor of 100 increases % dissociation by factor of
10
calc pH after add 35mL of 0.1M NaOH to 30mL of 0.1M HCN
11.89
What is the pH of a solution containing 0.028 mol of Be(OH)2 in 500. mL of water if we assume that all of it dissolves in the amount of water provided?
13.05
Calculate the amount of heat (in kJ) required to convert 86.6g of water to steam at 100°C. The molar heat of vaporization of water is 40.79kJmol.)
16.00+ (2* 1.008)= 18.016 g/mol (molar mass) Mol H2O= 86.6g/ 18.016= 4.8068 q= 4.8068mol (40.79 kJ/mol)= 196 kJ
For an X-ray crystallography sample, X-rays with a wavelength of 179 pm strikes a crystal, which reveals that the distance between the layers is 286 pm. Assuming n = 1, what is the angle needed for proper diffraction?
18.2°
Balance the following redox reaction! (6 points) Cr3+(aq) + Cl2(g) + H2O(l) → Cr2O72-(aq) + Cl-(aq) + H+(aq) How many total electrons are transferred in the above redox reaction?
2 Cr3+(aq) + 3 Cl2(g) + 7 H2O(l) → Cr2O72-(aq) + 6 Cl-(aq) + 14 H+(aq) 6
Consider the titration of 100.0 mL of 0.06 M HOCl (Ka = 3.5 x 10-8) with 0.0400 M NaOH. How many milliliters of 0.0400 M NaOH are required to reach the equivalence point? Calculate the pH: 1. After addition of 10.0 mL of 0.0400 M NaOH (answer) 2. Halfway to the equivalence point (answer) 3. At the equivalence point. (answer)
2. 7.46 3. 9.92
At 150 °C the reaction X(g) + 2Y(g) ⇋ 2Z(g) has a KC value of 0.0713. Calculate Kp at the same temperature for this reaction.
2.05×10-3 KP = (RT)^∆n
The rate constant of a first-order reaction is 9.80 × 10-3 min-1 at 303 K. What is the rate constant at 323 K if the activation energy for the reaction is 126 kJ/mol?
2.17 × 10-1 min-1
What is the osmotic pressure of a solution formed by dissolving 25.0 mg of aspirin (C9H8O4), molar mass 180.15 g/mol, in enough water to make 0.150 L of aqueous solution at 25°C?
2.26 × 10-2 atm
It takes 218hrs for Ea of a certain radioactive isotope to fall o one-tenth of it original value. Calc half life
21.8 h
X-rays of wavelength 154 pm strike an aluminum crystal; the X-rays are reflected at an angle of 19.3°. Assuming n = 1, calculate the spacing between the planes of aluminum atoms in pm that is responsible for this angle of reflection.
233. pm
The vapor pressure of t-butyl chloride, (CH3)3CCl is 760.0 torr at 76.9°C and 101.0 torr at 24.9°C. What is ΔHvap of t-butyl chloride?
33.7 kJ/mol
One step in the manufacture of sulfuric acid is the oxidation of sulfur dioxide:2 SO2(g) + O2(g) ⇌ 2 SO3 (g)If KP for this reaction is 3.50 at 1000 C, what is the value of Kc at the same temperature?
366 KP = Kc (RT)n n = -1 Kc = KP R T = 3.500.082061273 = 366
Aluminum crystalizes with a face-centered cubic unit cell and has a density of 2.71 g/cm3. Calculate the atomic radius of an Al atom in angstroms (Å).
386.1 A
Given values of ∆G°f at 25°C for liquid ethanol (-174.9 kJ/mol) and gaseous ethanol (-168.6 kJ/mol), calculate the vapor pressure of ethanol at 25 °C.
6.3 kJ
Determine the equilibrium constant for the system N2O4 ⇋ 2NO2 at 25°C. The concentrations At equilibrium are: [N2O4] = 2.54 × 10-2 M, [NO2] = 1.41 × 10-2 M.
7.83 × 10-3
Calculate the pH in a 1.5 M NaNO2 solution (Ka = 4.5 x 10-4)
8.76
How many grams of PbSO4 are reduced at the cathode if you charge a lead storage battery for 1.50 h with a constant current of 10.0 A?
84.9
G°=
= ΔH - TΔS
exergonic reaction
A spontaneous chemical reaction in which there is a net release of free energy.
Brønsted-Lowry:
Acids are proton (H+) donors, bases are proton acceptors.
Which of the following salts will produce an acidic solution?(A) Al(NO3)3B) KCNC) NaClO4D) RbNO2
Al(NO3)3
examples of molecular crystals
Ar, CO2, I2, H2O, C12H22O11 water and benzene
Calculate the pH of a buffer prepared by adding 0.25 mol of NaNO2 to 1 L of 0.50 M HNO2 (assume no volume change)! Ka(HNO2) = 4.5 × 10-4
Buffer: Henderson Hasselbalch equation pH = pKa + log[base]/[acid] pKa = -logKa = 3.35 [base] = [NO2-]= 0.25M [acid] = [HNO2] = 0.5 M pH = 3.35 + log(0.25/0.5) = 3.05
Change in Pressure/volume on equilibrium
Decreasing the volume (increase P) shifts the equilibrium toward the side with fewer moles of gas.
What happens to E when new bonds are formed?
E released
T(K): k(s-1) 300 : 3.9x10-2 310 : 1.1x10-1 320 : 2.8x10-1 What is Ea and rate constant at 80C
Ea= 80 kJ/mol k=4.8 s-1
E°cell=
Ecathode - Eanode
E equation using E°
E°- 0.0592v/n log Q (most likely a free response question)
Kc = Kp when ∆n = 1
FALSE Kp= Kc(RT)Δn
The units of the reaction rate depend on the reaction order.
False
pH can only be within 0-14
False
When dissolving an ionic compound in water the change of entropy is always positive.
False - Normally true but has an exception: if dissolving an ionic compound in water with ion charge >= 2+, 2- the change is entropy is < 0 - Solids usually dissolve better in liquids at higher temps
For the reaction: 2 A(g) + B (g) <=> 2 C (g) H = + 58 kJ The concentration of C increases when the volume of the container is increased.
False 3 mol gas on reactant side and 2 mol gas products more space, so shift left to more moles
For the reaction: 2 A(g) + B (g) <=> 2 C (g) H = + 58 kJ The concentration of C increases when a catalyst is added.
False Catalyst speeds up reaction, no shift
In an electrolytic cell, a spontaneous chemical reaction generates and electric current.
False Galvanic cell, voltaic cells -> spontaneous Electrolytic cell -> Nonspontaneous
A solution of 1 M HNO2 will has [H3O+] = 1 M.
False HNO2 is WA and needs Ka to solve for how much H3O Ka: HNO2 + H2O <-> H3O + NO- 2
For a mixture of two volatile liquids with different boiling points, the relative molar amounts are the same in the liquid and vapor phase.
False If liquid A has lower bp If you start with Xa = 0.5 and Xb= 0.5 more A will vaporize so more A will be in the gas phase
Adding 0.10 M NaOH to a 0.20 M solution of CH3COONa will form a buffer.
False NaOH is SB and CH3COONa is WB -> a mixture of SB and WB does not form buffer
A dynamic equilibrium is established when the concentration of reactants is equal to the concentration of the products.
False Rate forward= reverse No net change in concentration over time
The voltage of individual half-reactions can be measured independently.
False Run all with same standard (SHE)
The stronger the acid, the higher the pKa and the lower the Ka.
False Stronger acids have larger Ka and smaller pKa
Half-way to the equivalence point in a titration of a strong acid with a strong base, the pH is equal to the pKa of the acid.
False This is for titrations of WA and SB or WB and SA because a buffer is formed before equivalence point pH= pKa + log(WB/conjugate acid) WB and CA are equal half way to equiv. point so pH= pKa
At room temperature, H2O (l) H2O (s) is consistent with: H < 0, S < 0, and G < 0.
False Water freezes at 0 C ΔG depends on temp! must be lower than freezing point to be spontaneous so ΔG>0
If a transition metal complex absorbs green light it will appear green.
False We see the light that goes through, not the light that is absorbed
The entropy of any substance at 0 K is zero.
False must be crystalline solid with a perfect pattern, no mistakes, at 0K to have entropy of 0 (3rd law)
If G > 0, than Q < K
False ΔG >0 spontaneous in reverse Q< K goes forward spontaneously to equilibrium
If Ssystem is positive, G must be negative.
False ΔG= ΔH- TΔS (all system) ΔG also depends on ΔH
If Hsystem is positive and Ssystem is negative, G is negative at all temperatures.
False ΔH>0 unfavorable ΔS<0 unfavorable ΔG>0 all temps -- system only ΔG (-) = ΔH (+) - TΔS (-)
Solubility increases with increasing temperature for both solids in liquids and gases in liquids.
Fasle Gases dissolve better in liquids at lower temps; solids at higher
half life reactions
For a zero-order reaction, the half-life is dependent on the initial concentration. Each successive half-life is half as long as the preceding one. decreases as time proceeds For a first-order reaction, Successive half lives for a first order reaction are identical! For a second-order reaction, the half-life is dependent on the initial concentration. Each successive half-life is twice as long as the preceding one.
G equation using Ecell
G= -nFE
G equation using G°
G° + RT lnQ
Give the relationship between G° and K:
G° = -RT ln(K)
Give the relationship between G° and E°
G° = -nFE°
Electrolysis of aqueous NaCl yields Na(s) and Cl2(g).
H2O-> H2(g) + OH- (aq) Na+ (uncharged) Cl- -> Cl2(g)
strong acids examples
HCl Hydrochloric acid HBr Hydrobromic acid HI Hydroiodic acid HNO3 Nitric acid H2SO4 Sulfuric acid (only 1st proton) HClO4 Perchloric acid HClO3 Chloric acid
What is the Brønsted-Lowry acid in the following reaction that corresponds to the provided Ka? HF (aq) + H2O (l) ⇋ H3O+ (aq) +F- , Ka = 3.5 × 10-4
HF
General properties, cohesive forces, and examples of covalent crystals
Hard, brittle, high melting point, poor conductor of heat and electricity covalent C (diamond), *SiO2 (quartz)
Mercury, a liquid metal at room temperature, is known for its toxicity. The safe exposure limit for mercury is considered to be 0.1 mg/m3, which corresponds to a partial pressure of 1.2 10-8 atm. The following thermodynamic data are provided: Gf(Hg(l)) = 0 kJ/mol; Gf(Hg(g)) = 31.85 kJ/mol. Calculate the vapor pressure of mercury at room temperature. Assuming that enough mercury is spilled to achieve the equilibrium vapor pressure, is it necessary to stop working and evacuate the room?
Hg(l) ⇌ Hg(g) KP = P(Hg) Gf 0 31.85 kJ/mol G = Gf(products) - Gf(reactants) = 31.85 kJ/mol G = -RT ln(K) K = exp(-G/RT) = exp(-31,850 J/mol/{(8.314 J mol-1 K-1)·298 K}) = 2.61 10-6 P(Hg) = 2.61 10-6 atm Yes, the room should be evacuated.
For poorly soluble compounds, a precipitate is formed when
IP>Ksp
Lead storage batteries are rechargeable and therefore never need replacement.
If the product PbSO4 (s) is dislodged from the electrodes it cannot be used to recharge
Do you use Ka or Kb when solving for titration of WA and SB?
Ka
The pH of a 0.12 M solution of an acid HA is determined to be 2.62. What is the Ka for this acid?(Hint: do not disregard x).
Ka = [H3O+]eq[A-] eq /[HA]eq = x2/0.12 - x pH = 2.62 =-log[H3O+], [H3O+] = 10-pH = 2.39 × 10-3 M = [A-] [HA]eq = [HA]in - [A-] = 0.12 - 2.39 × 10-3 = 0.11761 M Ka = (2.39 × 10-3)2/ (0.12 - 2.39 × 10-3) = 5.71 × 10-6/0.11761 Ka = 4.85 × 10-5 4.9x10^-5 also acceptable
Calculate the pH of a 0.40 M solution of NaNO2. Ka(HNO2) = 4.5 × 10-4
Kb = Kw/Ka = 2.22 10-11 Na= no effect on pH Do a RICE box Assume: x << 0.40 2.210-11 x2/0.40 x = 3.010-6 << 0.40 assumption okay pOH = -log[OH-] = -log 3.010-6 = 5.53 pH = 14 - pOH = 8.47
Kp equation
Kp=Kc(RT)^delta n
Calculate molar solubility of Mn(OH)2 (Ksp (Mn(OH)2) = 2.1 x 10−13).
Ksp = [Mn2+][OH-]2 Mn(OH)2(s) -> Mn2+(aq) + 2 OH-(aq) 2.1 10-13 = x(2x)2 = 4x3 x = 3.7 10-5
What is the name of the principle that predicts how an equilibrium will shift in response to an external stress?
Le Chatelier
When placing compounds from lowest to highest IMF, What is an important thing to remember to do?
Look at molecular weight
What is the cell potential for the following reaction at 25 °C for [Fe2+] = 3.40 M and [Mg2+] = 0.310 M? Mg(s) + Fe2+(aq) → Mg2+(aq) + Fe(s)
Mg(s) Mg2+(aq) + 2 e- E° = 2.37 V Fe2+(aq) + 2 e- Fe(s) E° = -0.45 V E°cell = 2.37 V - 0.45 V = 1.92 V Nernst equation: E = E° - 0.0592 V/n · log(Q) Q = [Mg2+]/[Fe2+] = 0.31/3.4 = 0.0911 E = 1.92 V - 0.0592 V/2 · log(0.0911) = 1.95 V
how to determine if a salt will make solution neutral, basic, or acidic
N: cation- SB and anion- SA B: anion- conjugate base of WA A: cation is conjugate acid of WB
vapor pressure lowering equations
Psoln = Psolv Xsolv (Raoult's law) Ptotal = PA + PB = P°A XA + P°B XB ΔP = P°solv - P°solv = Xsolute P°solv partial P of solvenrt over solution, P°, is given by VP of the pure solvent, p1, times mole fraction of solvent in solution, X1 => p1=X1(P0)
What is a sequence of molecular events, or reaction steps, that defines the pathway from reactants to products, called?
Reaction mechanism
Steric Requirement
Relative orientation of the reactants must allow formation of any new bonds necessary to produce products. Explains why the number of reactions is much less than the number of collisions
entropy equation using Boltzmann
S= klnW k= boltsmann constant w= different ways molecules can be arranged-> W= X^n
Q < Kc
Some reactants still must convert to products to reach equilibrium reactants will decrease shift right
How much heat is needed to convert 776.g of ice at −10.0°C to steam at 126.0°C? Round your answer to 4 significant digits. Specific Heat For: Solid 2.03J·g°C Liquid 4.184J·g°C Gas 1.99J·g°C
Step 1: Warming ice to the melting point. q1=msΔt= 776.g(2.03J·g°C)[(0.0−10.0°C)(1kJ/1000J)]= 15.753...kJ Step 2: Melting ice at 0.0°C q2=(776.g)(1mol/18.02g)(6.01kJ/1mol)= 258.81...kJ Step 3: Heating water from 0.0°C to 100.0°C q3=msΔt= (776.g)(4.184J·g°C)(−100.00.0°C)(1kJ/1000J)= 324.68...kJ The total amount of heat is: q=+q1+q2q3= 15.753kJ+258.81kJ+324.68kJ= 599.24...kJ To calculate the amount of heat required to convert water at 100.0°C to steam at 100.0°C (vaporization), calculate the number of moles of water present and use the molar heat of vaporization: qvap= (776.g)(1mol/18.02g)(40.65kJ/1mol)= 1750.5...kJ Heating steam from 100.0°C to 126.0°C =qheat=msΔt= (776.g)(1.99J·g°C)(126.0-100.0°C)(1kJ/1000J)= 40.150...kJ =qtotal+q1+q2+q3+q4q5 =qtotal=+15.753kJ+258.81kJ+324.68kJ+1750.5kJ+40.150kJ = 2390.kJ
Dissolving 0.0250 g of β-carotene in 1.50 g of camphor gives a freezing point lowered by 1.17 °C. What is the molar mass of β-carotene? (Kf for camphor is 37.7 °C kg/mol)
Tf= iKp m 1.17= 37.7(x/0.0015)(1) x= 4.66x10^-5 mol molar mass= 0.025g/ 4.66x10^-5 mol= 537g/mol
If an elementary reaction is exothermic, then a. The activation energy for the forward reaction is smaller than that for the reverse reaction. b. The sum of activation energies gives the value of H for the reaction. c. The activation energy for the forward reaction is larger than that for the reverse reaction. d. The activation energy for the forward reaction is positive, and for the reverse reaction, negative. e. The activation energy for the forward reaction is negative, and for the reverse reaction, positive.
The activation energy for the forward reaction is smaller than that for the reverse reaction.
Osmotic Pressure (Π)
The amount of additional pressure caused by the water molecules moving back into the solution to stop osmosis Π = M · R · T M = Molarity R = Gas constant, 0.08206 (L⋅atm)/(mol⋅K) T = Absolute temperature
[A]0 -> products rate= k[A]2 How does k affect A
The larger k is, the more A is used up
vapor pressure lowering
The lowering of vapor pressure of a solvent by the addition of a nonvolatile solute to the solvent. Vapor pressure drops when solute molecules displace solvent molecules at the surface.
Henry's Law
The solubility of a gas is proportional to the partial pressure of the gas over the solution -> Solubility = C = k P (C is concentration of dissolved gas, k is henrys constant and P is pressure in atm)
Conjugate acid-base pairs can never differ by more than one H+.
True
Face-centered cubic is the same as cubic close-packed
True
For a zeroth order reaction a plot of [A] vs time is linear.
True
SiO2(s) is an example of a covalent network solid.
True
[Co(NH3)5Cl]Br and [Co(NH3)5Br]Cl are ionization isomers
True
Rate vs. [A]o data, [A] vs. time data, and half-life data are 3 ways to determine the order with respect to A.
True 1. Rate law: change [reactant] how does this change rate? 2. Plot [] vs. time, ln [] vs. time, and 1/[] vs. time, look for linear plot 3. What is pattern for half life?
Formation of a complex ion can increase the solubility of AgBr(s) in water.
True AgBr <-> Ag+ + Br- - Ag+ remove by reacting it away Ag+ + nNH3 -> Ag(NH3)+ n
Arrhenius, Bronsted-Lowry, and Lewis are 3 different models for acids and bases.
True Arrhenius: acid dissociates to give H and bases to give OH Lowry: acids are proton donor and base proton acceptor Lewis: acids electron pair acceptor and bases donor
The solubility of Ag2CO3 in water will increase when 0.1 M HCl is added.
True Co2- 3 is basic anion and will react with HCl Ag2CO3 <-> 2Ag+ + CO2- 3 <- reacts with acid so shifts right to make more dissolved ions
The maximum oxidation state chromium can adopt is +6.
True Cr is an early transition metal Max. oxidation state is equal to the group # Cr(Grp 6B) so 6+ is max.
An oxidizing agent gets reduced.
True Fe3+ is the oxidizing agent
For the reaction: 2 A(g) + B (g) <=> 2 C (g) H = + 58 kJ The concentration of C increases when the temperature is increased.
True Heat + 2A + B <-> 2C endothermic ΔH>0 add heat shift right, more products, increase K
If Q > K, the reaction proceeds from right to left.
True If Q> then too many products
pKw = pKa + pKb.
True Kw= Ka*Kb - logKw= - logKa - logKb
The following aqueous solutions are all acidic: AlCl3, CO2, and NH4NO3.
True NH+ 4 + H2O <-> NH3 + H3O Al(H2O)^3+ 6 + H2O <-> Al(H2O)5(OH)^2+ + H3O CO2 + H2O <-> H2CO3
HOCl is a stronger acid than HOI.
True Oxoacids -> most acidic, most electroneg. center atom
The units of the rate constant, k, depend on the order of the reaction.
True Rate= k [A][B]2 - rate= M/s - k= need 1/s*M2 - [A]= M - [B]2= M^2 must be same on both sides!
The vapor pressure of a pure solvent is higher than the vapor pressure of a solution containing a non-volatile solute.
True VP lowering for solutions less solvent can go from l to g with solute particles in the way
Molarity and density are temperature dependent
True Volume changes with T both M and D involve volume
The most common oxidation states adopted by late transition metals are +2 and +3.
True ex. Fe 3+, Fe2+, Fe+ Zn2+, Pt2+
For the reaction: 2 A(g) + B (g) <=> 2 C (g) H = + 58 kJ The concentration of C increases when C is removed.
True remove product, shift to replace it (right)
G and Ecell change as a reaction proceeds to equilibrium.
True ΔG= ΔG° + RT lnQ Ecell= E°cell - (0.0592v/n)logQ
Increasing temperature can change whether a reaction is spontaneous or not.
True ΔG= ΔH- TΔS If ΔH <0 and ΔS<0, spontaneous at low T only If ΔH>0 and ΔS>0, spontaneous at high T only
A right-handed helix is chiral.
True (OMIT)
For a polyprotic acid Ka1 > Ka2 in all cases.
Ture 1st dissociation is greatest
what happens to VP if two volatile liquids are mixed
VP is larger than VP of either- more collisions
Le Chatelier's Principle
When a stress is applied to a system at equilibrium, the system will respond by shifting in the direction that minimizes the effect of the stress. Shift right increases forward rate, which increases concentrations of products Shift left increases reverse rate, which increases concentrations of reactants
zero order
[A]t = -kt + [A]0 m/s changing concentration of reactant has no effect on rate t1/2 = [A]0 / 2k
what is % dissociation if pH= 2.5 for a 0.25M CH3COOH solution
[H3O]/[CH3COOH] [H3O]= 10^-2.5= 3.2x10^-3M 3.2x10^-3/ 0.25 x 100%= 1.3 (x is really small)
Ksp =
[prodA][prodB]
Volatility is
a measure of how readily a substance vaporizes
Elementary Reaction (step):
a single step in a reaction mechanism
galvanic (voltaic) cell
a spontaneous redox reaction generates a flow of electricity doesn't generate current
Platinum (Pt) crystallizes in a face-centered cubic unit cell with an edge length of 392 pm. a) How many atoms per unit cell are there? b) Calculate the density of copper in g/cm3
a) 4 b) 21.5 -> (4/ 6.022x10^23)(195.08 g/mol)= x -> (392 pm)^3(10^-30 cm3/ 1 pm3)= y -> x/y = answer
The thermal decomposition of phosphine into phosphorous and molecular hydrogen follows first-order kinetics. 2PH3 (g) → 2P (s) + 3H2 (g) At 680° C the rate constant for this reaction is 0.0198 s-1. a) Write out the integrated rate law for a first-order reaction b) In seconds, how long will it take for an initial concentration of 0.570 M to fall to 0.0130 M?
a) first: ln[A]t = -kt + ln[A] b) 191
A 0.0200 M formic acid solution has a pH of 2.74. Formic acid is a weak monoprotic acid and the equilibrium equation of interest is: HCOOH (aq) + H2O (l) ⇋ H3O+ (aq) + HCO2 - (aq) a) Write the Ka expression b) Set up the RICE table in terms of x c) Determine the value for x d) Calculate the acid dissociation constant for formic acid under the conditions described above.
a) 𝐾𝑎 = [𝐻3𝑂 +][𝐻𝐶𝑂2 −]/ [𝐻𝐶𝑂𝑂𝐻] b) pic c) [H3O+ ] = 10-2.74 = 1.82 × 10-3 M = 1.8 × 10-3 M d) 𝐾𝑎 = 1.8 × 10−4
At 400 K, the equilibrium constant for the following reaction is Kp = 7.0. Br2 (g) + Cl2 (g) ⇋ 2 BrCl (g) a) Write the Kp expression b) A closed vessel is charged with 1.00 atm of Br2 (g), 1.00 atm of Cl2 (g), and 2.00 atm BrCl. In which direction does the reaction proceed to achieve equilibrium? Provide the appropriate calculation(s) to support your choice and circle your final answer at the bottom of the page.
a) 𝑄𝑝 = 𝑃𝐵𝑟𝐶𝑙 2 / 𝑃𝐵𝑟2 𝑃𝐶𝑙2 _ b) 𝑄𝑝 = [2.00] 2 [1.00][1.00] = 4.00 < 7.0 Q < K = right
A proposed two-step mechanism is shown below. H2O2 (aq) + Br- (aq) → H2O (l) + OBr - (aq) Slow H2O2 (aq) + OBr- (aq) → H2O (l) + Br- (aq) + O2 (g) Fast a) What is the overall reaction? b) Which chemical is a reaction intermediate? c) What is the overall rate law for this mechanism?
a. 2H2O2(aq) → 2H2O(l) + O2(g) b. OBr-(aq) c. rate = k[H2O2][Br- ]
What is a compound that is insoluble at neutral pH, but soluble at both high and low pH, called?
amphoteric
Which group includes only exothermic processes? a. freezing, vaporization, deposition b. freezing, condensation, deposition c. melting, condensation, deposition d. melting, evaporation, sublimation e. melting, condensation, sublimation
b. freezing, condensation, deposition
Lewis base vs Lewis acid
base- donates e- pair acid- accepts e- pair
find pH by adding 0.05mol sodium acetate to 1L of 0.1M acetic acid. Ka (acetic acid)= 1.8x10^-5
before the ionization of the weak acid H3O+ is 1x10^-7 M, but it is insugnificant so its neglected1) 1.8x10^-5= x(0.05+x)/ (0.1-x)x is assumed to be very small-->> 1.8x10^-5= 0.05x/ 0.12) x= 3.6x10^-5M so [H3O+]=x therefore pH = -log(x)= 4.443) 3.6x10^-5/0.1 x100= 0.036% this is much smaller than percent ionization prior to addition
electrolytic cell
cell that uses electrical energy to produce a chemical change that would otherwise not occur spontaneously
How can we know the atomic level structures of solids?
crystallography
Which choice is an example of a network solid? a. NaCl b. crystal c. iron d. quartz e. glass
d Examples of network solids include diamond with a continuous network of carbon atoms silicon dioxide or quartz with a continuous three-dimensional network of SiO 2 units. Graphite consists of continuous two dimensional layers covalently bonded within the layer with other bond types holding the layers together.
A positive slope for a region of a heating curve indicates that _________ in that region. a. no energy is being absorbed by the system b. energy is being given off by the system, but it cannot be measured c. energy is being absorbed by the system and is being used for a phase change d. additional data is needed to explain this observation e. energy is being absorbed by the system and is being used to increase the temperature
e. energy is being absorbed by the system and is being used to increase the temperature
Endogonic (Endothermic)
energy absorbing have high Ea
Q = Kc
equilibrium
Addition of Reaction Components shift
equilibrium to shift to the opposite side of the reaction, WITHOUT changing K.
strong acid-strong base titration claculation
fist find moles for both substances then find what is left after neutralization by subtracting moles then find the M using moles remaining and total volume which is M for H3O+. plug that in to find pH.
In kidney dialysis, the diffusion of solvent particles takes place across a semipermeable membrane from an area of ______________ (higher / lower) to _________________ (higher / lower) solvent concentration.
higher; lower
van't Hoff Factor, i:
i = Actual number of particles in solution after dissociation/ number of formula units initially dissolved in solution
Acid Strength Trend
increase right and down higher electronegativity= stronger increases with oxidation number of central atom (# O atoms)
A reaction was found to be first order in carbon dioxide concentration. If all else is kept the same, the rate of reaction _______ (select one: increases, decreases, remains unchanged) by a factor of _________ (whole number) if the [CO2] is doubled.
increases; 2
Vapor pressure and boiling point relationship
inversely related
rate constant (k) equation
k = Ae-Ea/RT where A is a constant, known as the Arrhenius constant, Ea is the activation energy and T is the temperature in K. 1. lnk=(-Ea/R)(1/T)+lnA 2. lnk1/k2= Ea/R(1/T2- 1/T1)
A certain reaction has Ea of 83 kJ/mol. If the rate constant is 2.1x10-2 s-1 at 150C, what is rate constant at 300C
k2= k1/(e^(Ea/R)(1/T2-1/T1)) rate constant is 10 s-1
Arrhenius equation
k=Ae^(-Ea/RT) R= 8.314
Clausius - Clapeyron equation:
ln(p1/p2)=(ΔHvap/R)(1/T2-1/T1) P= (-∆Hvap/ R) (1/T)+C
first order
ln[A]=-kt+ln[A]0 t1/2 = 0.693/k s-1 the reaction rate is directly proportional to the concentration of only one reactant
Catalysts work by allowing the reaction to proceed via an alternate pathway with a ___________ activation energy.
lower Arranges particles in position more likely to react. Catalysts can make reactions go thousands, even millions, of times faster! the presence of a catalyst does not affect the energy difference between the reactants and the products, but the transition state changes.
Exothermic means PE is _______ Endothermic means PE is ______
lowered (desirable!) higher
mmHg to kPa
multiply by 101.325/760
Q > Kc
net reaction goes to left (products to reactants) Too many products
can both Ssys and Ssurr be negative
no
Q<Ksp
no precipitate forms
Q=Ksp
no precipitate forms
Bragg equation
nλ = 2d sin θ
Bragg's Law Equation
nλ=2dsinθ
equivalence point
occurs when the moles of acid equal the moles of base in a solution the point in a titration where the number of moles of hydrogen ions equals the number of moles of hydroxide ions
Q>Ksp
precipitate forms
The plasible mechanism for H2+ 2IBr-> I2+ 2HBr is: Step 1: H2+ IBr-> HI+ HBr (slow) Step 2: HI+ IBr-> I2+ HBr (fast) Whats the rate law
rate=k[H2][IBr]
Melting, vaporization and sublimation _______ heat energy to break attractive interactions, freezing, condensation and deposition __ heat energy
required released
Finding atomic radius from edge a length of cubic cell
scc: a = 2rbcc: a=4r/ √3fcc: a=√8r
coordination number for each cubic cell
scc= 6, bcc= 8, fcc= 12
Spontaneous vs Nonspontaneous
spontaneous -G, exergonic, under a specified set of conditions. nonspontaneous +G, Endergonic
A solution in which there is more dissolved solute than in a saturated solution is known as a(n) _____________ solution.
supersaturated
The decomposition of aqueous hydrogen peroxide to gaseous O2 and water is a first-order reaction. If it takes 8.0 h for the concentration of H2O2 to decrease from 0.80 M to 0.40 M, how many hours are required for the concentration to decrease from 0.60 M to 0.10 M?
t= 21hrs
What is the only thing that will change the value of Kc?
temp
The average osmotic pressure of blood is about 7 atm. Therefore ___.
the pressure of about 7 atm would be required to prevent osmosis if blood is in contact with pure water accross a semipermeable membrane.
Rate-Determining Step:
the slowest step in a reaction mechanism
Reaction Mechanism:
the step-by-step sequence of reactions by which the overall chemical change occurs
N2 + O2(g) < = > 2 NO(g), Kc = 1.7 x 10-3 at 2300 K. If the initial concentration of N2 and O2 at 2300 K are both 1.40 M, what are the concentrations of NO, N2, and O2 when the reaction mixture reaches equilibrium?
x= 2.83x10^-2 [NO]= 5.66x10^-2
Calculate the molar solubility of MgF2 in 0.10 M NaF at 25°C. Ksp (MgF2) = 7.4 x 10-11.
x= 7.4x10^-9
ΔG equation
ΔG= ΔG0 + RT lnQ R= 8.314
boiling point elevation equation
ΔTb=Kbm
freezing point depression equation
ΔTf = Kfm
