Chad missed q
If 10J of work is performed by the system on the surroundings and 18J of heat is transferred from the surroundings to the system, what is the change in the internal energy of the system?
+8 kJ
If the rate of disappearance of Cu2+ is 0.75M/min, then what is the rate of appearance of Al3+? 2Al + 3Cu2+ --> 2Al3+ + 3Cu 0.25M/min 0.50M/min 0.75M/min 1.13M/min
0.50M/min The mole to mole ratio between Cu2+ and Al3+ is 3:2. This means that for every 3 moles of Cu2+ that are consumed, 2 moles of Al3+are produced. So if the rate of disappearance of Cu2+ is 0.75M/min, then the rate of appearance of Al3+ must be 2/3 as much or 0.50M/min.
The molar solubility of FePO4 is 1.1x10-11. What is Ksp? 1.2x10-22 4.1x10-53 5.3x10-33 3.3x10-6
1.2 x 10^-22 molar solubility = x Ksp = x^2 (in this case) Ksp = (1.1x10-11) ^ 2
What is the pH of 0.02M NH2NH2 (Kb = 8.5x10-7)? 9. 10.1 11.2 12.2
10.1 [OH-] = sqrt (Kb x [A-])
If 92g NO2 and 48g O2 react completely, what is the maximum number of grams of N2O5 that could be produced? 4NO2 + O2 --> 2N2O5 92 108 324 432
108 1. find limiting reagent --> NO2 2 NO2 mol x ( 2 N2O5 / 4 NO2) x (108 g N2O5 / mol) = 108 g of N2O5
How much heat is released when 120g of Ca(s) reacts completely with excess O2(g)? 2Ca(s) + O2(g) → 2CaO(s) Latex Formula = -1271kJ 1907kJ -3813kJ 3813kJ -1271kJ
1907 kJ 120 g Ca x ( 1 mol Ca / 40 g Ca) x (1270 kJ released / 2 mol Ca) = 1907 kJ the question specifies heat RELEASED, indicating the negative sign in context
1 atm = ___ torr = ___ mmHg
760, 760
What is the molar solubility of a salt of the formula AB3 (Ksp=3.0x10-19)? 1.8x10-5M 1.0x10-5M 5.5x10-10M
AB3(s) → A3+(aq) + 3B-(aq) Ksp=[A3+][B-]3 = (x)(3x)3 = 27x^4 = 3.0x10-19 30x10^-20 = 27 x^4 x4=1.1x10-20 x=(1.1x10-20)1/4 x~1.0x10-5=molar solubility
What is the net ionic equation for the reaction between aqueous silver nitrate and aqueous potassium chloride? AgNO3(aq) + KCl(aq) → AgCl(s) + KNO3(aq) Ag+(aq) + Cl-(aq) → AgCl(s) K+(aq) + NO3-(aq) → KNO3(s) Ag+(aq) + Cl-(aq) + K+(aq) + NO3-(aq) → AgCl(s) + K+(aq) + NO3-(aq)
Ag+(aq) + Cl-(aq) → AgCl(s) AgNO3(aq), KCl(aq), and KNO3(aq) are strong electrolytes and so the ionic equation is Ag+(aq) + Cl-(aq) + K+(aq) + NO3-(aq) → AgCl(s) + K+(aq) + NO3-(aq) K+(aq) and NO3-(aq) are both spectator ions (as they appear on both sides of the reaction as free ions and therefore haven't done anything) and are eliminated to yield the net ionic equation: Ag+(aq) + Cl-(aq) → AgCl(s)
What volume of 10M HCl would be required for 200g CaCO3 to react completely? CaCO3(aq) + 2HCl(aq) --> H2(g) + CaCl2(aq) 20ml 80ml 400ml 800ml
C 200g CaCO3 x (1 mol CaCO3 / 100 g CaCO3) x (2 mol HCl / 1 mol CaCO3) = 4 mol HCL 10 M HCl = mol/ L 4/10 = L = 400 mL
If the vapor pressure of pure water at Latex Formula is 18 torr, what is the vapor pressure of water above a solution of 5.5m CH3OH? 12.4 torr 14.4 torr 16.4 torr 17.8 torr
C We are given the molality of the solution, the unit 'm' = moles of solute per kg of solvent (water in this case). So 5.5m CH3OH has 5.5 moles CH3OH for every 1kg H2O. 1 kg H2O --> 1000 g H2O / (mol/ 18g H2O) = 55.5 mol H2O (18 torr) [55.5 mol H2O / (55.5 + 5.5)] = 16;4
which of the following has the highest e- affinity Be B C N
C electron affinity = goes left to right N and Be = an exception bc either 1/2 or full shell
what are the 2 network covalent solids
Cdiamond + SiO2 (quartz)
which of the following result in the conversion of a proton into a neutron positron emission beta decay e-capture both positron emission and e-capture
D
A balloon is filled with equal amounts of Ar and Ne gases. Which gas will escape out of the balloon faster and why? Ar since it will have a larger kinetic energy Ne since it will have a larger kinetic energy Ar since it will have a smaller rms velocity Ne since it will have a larger rms velocity
D As both gases are in the same balloon it can be assumed they are at the same temperature and therefore have the same average kinetic energy eliminating choices A and B. With the same average kinetic energy, the lighter Ne will have a larger rms (like an avg) velocity which is why Ne escapes faster (choice D).
which is the quantum #s [n,l,ml,ms] for e- in 5f orbital A [5,4,0,-1/2] B [5,3,4,+1/2] C [4,3,-1,+1/2] D [5,3,-1,-1/2]
D bc f is 3
A balloon is filled with equal amounts of H2 and O2 gases. Which gas will escape out of the balloon faster and how many times faster? H2, 4 times faster O2, 4 times faster H2, 16 times faster O2, 16 times faster
H2, 4 times faster this uses Graham's law of effusion: r1/r2 = sqrt (M2/M1) rH2 / rO2 = sqrt (32/2) 32/2 = 16 sqrt 16 = 4
Which of the following is the strongest acid? H2O H2S H2Se H2Te
H2Te For binary acids, acid strength increases down the periodic table with increasing size (as a larger anion is a more stable conjugate base).
what are the strong 7 acids
HClO4, H2SO4, HI, HBr, HCl, HNO3, HCIO3
whic of the following elements has the highest Vapor pressure He Ne Ar Kr
He vp increases when intermolecular forces (or mass) decreases
which is an ionic compound NH4Br CO N2O4 SO2
NH4Br although its all nonmetal, it has a polyatomic ion (ammonium ion
highest bp? HOCH2CH2OH CH3CH2OH NaOH H2O
NaOH bc ionic/covalent >>>>
relationship of acidity w Ka and pKA
acidity INCREASES w Ka INCREASES n pKA DECREASES
what is the 1st ionization energy
the energy required to remove an e-
Which of the following would form a buffer solution? 0.1M HBr and 0.1M KBr 0.1M HClO4 and 0.1M KOH 0.1M HClO2 and 0.1M NaClO2 0.1M HF and 0.1M NaOH
0.1M HClO2 and 0.1M NaClO2 A buffer is the mixture of a weak acid with its conjugate base (or weak base with its conjugate acid) in as close to a 1:1 ratio as possible. eliminate B and D compare A + C... HBr is STRONG acid therefore answer is C
After a 50g piece of an unknown metal at 50oC is added to 50g of H2O(l) at 0oC, the mixture reaches thermal equilibrium at 10oC. What is the specific heat of the metal? (specific heat of water is 1cal/goC) 0.2 , 0.25, 5, 0.5 cal/goC
0.25 remember that delta T = final - initial so for metal its 10-50 water its 10-0
What is the molality of an aqueous solution of a non-electrolyte that has a freezing point of -0.62 oC (KF,water=1.86 oC /m)? 0.33m 0.75m 1m 1.5m
0.33 m freezing pt depresion eq: dTf = -iKf(m) i = 1 for non electroyltes -0.62 = -1 (1.86) m m = 0.33
Which of the following solutions will have the lowest freezing point? 1m NaCl 1.5m CH3CH2OH 0.7m AlCl3 1.2m CsNO3
0.7m AlCl3 The greater the concentration of solute, the greater the freezing pt. depression. 1m NaCl = 2m ions since NaCl dissociates into 2 ions 1.5m CH3CH2OH=1.5m as it is a non-electrolyte and doesn't dissociate. 0.7m AlCl3 = 2.8m ions since AlCl3 dissociates into 4 ions (1 Al3+ and 3Cl-) 1.2m CsNO3 = 2.4m ions since CsNO3 dissociates into 2 ions (1 Cs+ and 1NO3-)
How many moles of electrons are needed to produce 26.0 grams of chromium metal from the electrolysis of 1.0M CrCl3? 0.25 0.5 1.5 3
1.5 The half reaction in which Cr metal is produced is as follows: Cr3+ + 3e- --> Cr So it takes 3 moles of electrons to produce 1 mole of Cr. In this case were producing 26.0g of Cr which is 0.5 moles. Finally based on the 3:1 ratio of moles of electrons to moles Cr, it will require 3/2 moles of electrons to make 0.5 moles of Cr.
Which of the following solutions will have the highest freezing point? 1m NaCl 1.5m CH3CH2OH 0.7m MgCl2 1.2m CsNO3
1.5m CH3CH2OH The highest freezing pt. will be the one that has been depressed the least and therefore is the solution with the lowest concentration of dissolved species. NaCl dissociates into 2 ions (1 Na+ and 1 Cl-) and so 1m NaCl results in a 2m solution of dissolved species. 0.7m MgCl2 dissociates into 3 ions (1 Mg2+ and 2 Cl-) and so 0.7m MgCl2 results in a 2.1m solution of dissolved species. 1.2m CsNO3 dissociates into 2 ions (1 Cs+ and 1 NO3-) and so 1.2m CsNO3 results in a 2.4m solution of dissolved species. CH3CH2OH is non-electrolyte and doesn't dissociate into ions and therefore it's 1.5m concentration is the lowest concentration of dissolved species amongst the answer choices and this solution will have the smallest decrease (depression) in its freezing point leaving it with the overall highest freezing point.
Which of the following is a formation reaction? C(diamond) + O2(g) → CO2(g) N2(g) + H2(g) → 2NH3(g) C(graphite) + CO2(g) → 2CO(g) 1/2H2(g) + 1/2N2(g) +3/2O2(g) → HNO3(g)
1/2H2(g) + 1/2N2(g) +3/2O2(g) → HNO3(g) A formation rxn forms 1 mole of a single product (eliminates choices B and C) from individual elements in their standard states (eliminates choice A as the standard state of carbon is graphite). Only choice D is left to satisfy the definition of a formation rxn.
how many e- max can occupy the 3rd shell (n=3) of an atom?
18 bc 2n^2
what is the electron config of Cu+?
1s2 2s2 2p6 3s2 3p6 3d10 **Cu is an exception, also electrons are taken away from the highest energy lvl shell
The total pressure inside a vessel containing 0.1moles O2, 1.5moles Ar, and 0.4 moles Ne is 10atm. What is the partial pressure of Ne inside the vessel? 1 atm 2atm 4atm 5atm
2 atm
What is the pH of 0.2M HOCN (Ka = 3.5x10-4)? 0.7 2.1 3.5 4.2
2.1 [H+] = sqrt( 7x 10^-5)= sqrt (70 x 10^-6) = 8.4 x 10^-3 pH = -log [H+] = -log(8.4x10-3) = 2.1
To what volume of water should 50g of CaBr2 be diluted to make a 0.1M solution? 25ml 250ml 2.5L 4.2L
2.5 L We'll use the following equation for the definition of molarity: M = moles / VL where VL is the volume in liters Rearranging to solve for volume: VL = moles / M To solve well first have to convert 50g CaBr2 into moles: 50g CaBr2 (1mole CaBr2 / 200g CaBr2) = 0.25moles CaBr2 VL = moles / M VL = 0.25moles / 0.1M = 2.5L
If the pH is 6.6, what is the [H+] of the solution? 2.5x10-7M 6.6x10-7M 3.1x10-8M 7.4x10-6M
2.5x10-7M [H+] = 10-pH = 10^-6.6 which will be between 1.0x10-7M and 1.0x10-6M which still leaves us with 2 possible answer choices (2.5x10-7M and 6.6x10-7M) so well have to be more precise. Youll have to remember not only the [H+] values when the pH is an integer but also for the halves (.5) too. The half pH occurs when [H+] = 3.16x10-whatever as demonstrated below: [H+] = 1x10-6M pH = 6 [H+] = 3.16x10-7M pH = 6.5 [H+] = 1x10-7M pH = 7 Since a pH of 6.6 is between 6.5 and 7, the [H+] must be between 1x10-7M and 3.16x10-7M and therefore 2.5x10-7M must be the correct answer.
at STP, 1 mol = ___ L
22.4
If 9 moles Ba(OH)2 and 7 moles H3PO4 react completely, what is the maximum number of moles of Ba3(PO4)2 that could be produced? 3Ba(OH)2 + 2H3PO4 Latex Formula Ba3(PO4)2 + 6H2O 3 3.5 14 27
3 find limiting reagent by comparing MOL RATIOS (dont need to calculate bc theyve given moles) - 3 < 3.5 therefoe BaOH2 is LR 9 mol BaOH2 / (1 Ba3PO42 / 3BaOH2) = 3
The molar solubility of a salt of the formula MX2 is 2.0x10-6M. What is the Ksp? 8x10-18 4x10-12 1.6x10-17 3.2x10-17
3.2x10-17 MX2(s) → M2+(aq) + 2X-(aq) Ksp = [M2+][X-]2 = (x)(2x)2 = 4x3 Remember that the molar solubility = x and that were solving for Ksp, not the other way around. Ksp = 4(2.0x10-6)3 Ksp = 4(8.0x10-18) = 32x10-18 = 3.2x10-17
What volume of 0.2M NaOH is required to neutralize 30mL of 0.1M H2SO4? 15mL 30mL 60mL 120mL
30 mL nAMAVA = nBMBVB (2)(0.1M)(30mL) = (1)(0.2M)(VB) VB = 30mL
How much more acidic is pH 1.5 than pH 4.0? 2.5 times more acidic 25 times more acidic 300 times more acidic 2500 times more acidic
300x A difference of 2.5 pH units is a factor of 10^2.5 times more acidic. Since 10^2 = 100 and 10^3 = 1000, 10^2.5 must be between 100 and 1000, there is only one answer choice that falls in this range, pH 1.5 is approximately 300 times more acidic than pH 4.0.
If the activation energy of a reaction is 50kJ and ΔH=15kJ, what is the activation energy of the reverse reaction?
35 kJ bc Ea - dH = Ea of reverse
What is the pH of a solution that contains 0.003M HF and 0.02M NaF (Ka, HF=6.8x10-4)? 4.0 5.1 9.2 2.2
4.0 pH = pka + log [ A-]/[HA] pH = 3.2 + log 0.02/ 0.003 pH = 3.2 + log 10/1 pH= 3.2 + 1
Q. Sc3+ can be added to a solution of 0.0001M NaF to what maximum concentration before a precipitate forms (Ksp,ScF3 = 4.2x10-18)? 6.6x10-8M 1.1x10-6M 4.2x10-14M 4.2x10-6M
4.2x10-6M NaF is a strong electrolyte (all group 1 metal salts are) and dissociates completely resulting in a fluoride concentration of [F-] = 0.0001M. We can substitute this into the Ksp expression to figure out the maximum concentration of Sc3+ possible before a precipitate forms: Ksp = [Sc3+][F-]^3 4.2x10-18 = Sc3+[0.0001 M]^3 [Sc3+] = 4.2x10-18 / 1x10-12 [Sc3+] = 4.2x10-6M
What volume of CO2(g) is produced at STP when 200g of CaCO3 reacts completely with excess HCl? CaCO3(s) + 2HCl(aq) --> CaCl2(aq) + H2O(l) + CO2(g) 11.2L 22.4L 33.6L 44.8L
44.8 L One of the keys to this problem is to remember that 1 mole of gas at STP occupies 22.4L. Since the molar mass of CaCO3 is approximately 100g, we have 200g present in the reaction, and therefore 2 moles of CaCO3 react with excess HCl . From the balanced equation we can see that CaCO3 and CO2 are in a 1:1 ratio, so 2 moles of CaCO3 reacts to produce 2 moles of CO2, or (22.4L/mole) x (2 moles) = 44.8L.
Which of the following could be the pH at the equivalence point of the titration of NH3 with HCl? 5.2 7.0 9.1 10.6
5.2 NH3 is a weak base and HCl is a strong acid and the pH at the equivalence point of the titration of a weak base with a strong acid will be slightly acidic, a pH between 4 and 7 being typical. Only 5.2 is in this range and is the correct answer.
If the pH is 4.9, what is the [OH-] of the solution? 6.9x10-9M 8.6x10-8M 1.6x10-10M 7.9x10-10M
7.9x10-10M if the pH = 4.9, then the pOH = 9.1 [OH-] = 10-pOH = 10-9.1 which will be between 1.0x10-10M and 1.0x10-9M which still leaves us with 2 possible answer choices (1.6x10-10M and 7.9x10-10M) so well have to be more precise. Youll have to remember not only the [OH-] values when the pOH is an integer but also for the halves (.5) too. The half pOH occurs when [OH-] = 3.16x10-whatever as demonstrated below: [OH-] = 1x10-9M pOH = 9 [OH-] = 3.16x10-10M pOH = 9.5 [OH-] = 1x10-10M pOH = 10 Since a pOH of 9.1 is between 9 and 9.5, the [OH-] must be between 3.16x10-10M and 1x10-9M and therefore 7.9x10-10M must be the correct answer.
What is the mass (in grams) of 3.01x10^22 gold atoms? 0.05 9.9 99 990
9.9 3.01x10^22 gold atoms x (1 mol / 6.02 x 10^23 atoms) x (197 g gold/ mol) = 9.9
If the pressure on a sample of gas behaving ideally is tripled while simultaneously reducing the temperature from 273 C to 0C , what is the effect on the volume of the gas? It is 6 times smaller It is 6 times larger It is 50 times smaller It is infinitely smaller
A We can solve this by looking at the relationships we can form from the equation PV=nRT. Pressure and volume are inversely proportional, so tripling the pressure will reduce the volume to 1/3 of its original value. Volume and temperature are directly proportional but must be examined using the absolute (Kelvin) scale. The temperature is cut in half in reducing it from 546K (273oC) to 273K (0oC) which thereby cuts the volume in half. Taking into a account both the pressure and temperature changes (1/3x1/2) we conclude that the volume will be 1/6 of it's original value (i.e. 6 times smaller).
Identify the catalyst in the following reaction mechanism. A + 2B → C + D (slow) D + E → F + A (fast)
A A catalyst will not appear in the overall reaction as it as both a reactant and a product (it is not consumed in a reaction). It is most easily recognized as a reactant in an earlier step and a product in a later step. Only A qualifies.
Why do most reactions proceed more quickly at higher temperatures? Greater number of collisions at higher temperatures A decrease in the activation energy at higher temperatures Greater percentage of high energy collisions at higher temperatures A and C All of the above
A and C At higher temperatures, molecules have a greater average velocity and will therefore collide more often (answer choice A) and with a greater average energy (answer choice C). The activation energy however is independent of temperature which eliminates answer choice B.
NaI is added to a solution of 0.0002M Bi(NO3)3, so that the final concentration of NaI is 1.0x10-5M. Which of the following is true? (Ksp,BiI3=8.2x10-19) A precipitate forms because Qsp < Ksp A precipitate forms because Qsp > Ksp A precipitate will not form because Qsp < Ksp A precipitate will not form because Qsp > Ksp
A precipitate will not form because Qsp < Ksp BiI3(s) → Bi3+(aq) + 3I-(aq) Ksp = [Bi3+][I-]3 (at equilibrium) Qsp = [Bi3+][I-]3 (not necessarily at equilibrium) Qsp = (0.0002)(1.0x10-5)3 Qsp = (2.0x10-4)(1.0x10-5)3 = 2.0x10-19 which is < 8.2x10-19 Since Qsp < Ksp, the solution is below the saturation point and will not form a precipitate.
500ml of 2x10-5M AgNO3 is added to 500ml of 1x10-5M NaCl. Which of the following accurately describes the solution? (Ksp,AgCl=1.8x10-10) . A precipitate will not form because Qsp > Ksp A precipitate forms because Qsp < Ksp A precipitate forms because Qsp > Ksp A precipitate will not form because Qsp < Ksp
A precipitate will not form because Qsp < Ksp Mixing 500ml of 2x10-5M AgNO3 with 500ml of 1x10-5M NaCl dilutes both concentrations in half (You can use M1V1 = M2V2 to figure this out). These final concentrations after mixing are therefore 1x10-5M AgNO3 and 0.5x10-5M NaCl or 5.0x10-6M NaCl. AgCl(s) → Ag+(aq) + Cl-(aq) Ksp = [Ag+][Cl-] (at equilibrium) Qsp = [Ag+][Cl-] (not necessarily at equilibrium) Qsp = (1x10-5)(5x10-6) = 5x10-11 which is < 1.8x10-10 Since Qsp < Ksp, the solution is below the saturation point and will not form a precipitate.
Which of the following will affect the rate of a reaction? Reactant concentrations Catalyst Temperature All of the above
All of the above In looking at a rate law (Rate=k[A]^x) it is easy to see that reactant concentrations (that arent zero order) and anything that affects k will affect the rate of the reaction. The dependence of the rate constant upon the activation energy (influenced by a catalyst) and the temperature is demonstrated by the Arrhenious equation: k = Ae ^ (- Ea/Rt). And so we see that because both a catalyst and temperature will affect the rate constant they will also affect the rate as well so the answer is all of the above.
What is the maximum concentration of fluoride ions that could be present in 0.032M Ba(NO3)2 (Ksp,BaF2 = 3.2x10-8)? 1.0x10-3M 2.0x10-3M 5.0x10-4M 1.0x10-6M
BaF2(s) → Ba2+(aq) + 2F-(aq) Ksp = [Ba2+][F-]^2 3.2x10-8 = (0.032)[F-]^2 *0.032 is given from the Ba(NO3)2 and NO3 is completely soluble so Ba = 0.032 [F-]=1.0x10-3M
which of the following has the highest 3rd ionization energy Be B C N
Be bc its "3rd e-" is coree
Which of the following will affect the rate CONSTANT of a reaction? Reactant concentrations only Catalyst only Temperature only Both a catalyst and temperature Reactant concentrations, a catalyst, and temperature
Both a catalyst and temperature This one is a little tricky. In looking at a rate law (Rate=k[A]^x) it is easy to see that reactant concentrations (that arent zero order) and anything that affects k will affect the rate of the reaction. But while reactant concentrations affect the rate of the reaction, they do not affect k, the rate constant. The dependence of the rate constant upon the activation energy (influenced by a catalyst) and the temperature is demonstrated by the Arrhenious equation: k = Ae ^ (-Ea/ rt)
For which of the following reactions is ΔHrxn =ΔHf ? Na+(aq) + Cl-(aq) → NaCl(s) C(graphite) + 1/2O2(g) → CO(g) Na(s) + Cl(g) → NaCl(s) 1/2O2(g) + H2O(l) →H2O2(l)
C(graphite) + 1/2O2(g) → CO(g) A rxn for which ΔHrxn =ΔHf must be a formation rxn. A formation rxn forms 1 mole of a single product from individual elements (eliminates choice D as H2O is a compound not an element) in their standard states (eliminates choices A and C as the standard state of sodium is Na(s), the standard state of chlorine is Cl2(g)). Only choice B is left to satisfy the definition of a formation rxn.
which of the following has the greatest intermolecular forces CH4 CH3Cl CH2Cl2 CHCl3
CHCl3
Adding 5 moles of which of the following to 10L of water would result in the largest boiling point elevation (assume that all answer choices are all soluble in water? CaCl2 KCl CH3OH BaSO4
CaCl2 5mol CaCl2 = 15mol ions since it dissociates into 3 ions (1 Ca2+ and 2Cl-) 5mol Latex Formula = 10 mol ions since it dissociates into 2 ions (Latex Formula) 5mol KCl = 10 mol ions since it dissociates into 2 ions (Latex Formula) 5mol Latex Formula = 5mol Latex Formula since it is a non-electrolyte and doesn't dissociate into ions CaCl2 dissociates to give the highest concentration of ions and therefore has the highest boiling point elevation.
An aqueous solution of which of the following salts will have a pH closest to 7? NaHCO3 KClO2 CaCl2 Al(NO3)3
CaCl2 This question test knowledge of the potential acidity/basicity of salts. Cations: Group 1 and 2 metal ions or metal ions with a +1 charge are negligible; all other cations are acidic. Anions: The general rule is the that conjugate base of a strong acid is a negligible base (Cl-, Br-, I-, NO3-, ClO4-, ClO3-) or an acid (in the case of HSO4-). But almost all other anions are basic. NaHCO3: Na+ is negligible (Group 1) but HCO3- is a base (Overall: Basic Salt) KClO2 : K+ is negligible (Group 1) but ClO2- is a base (Overall: Basic Salt) CaCl2: Ca2+ is negligible (Group 2) and Cl- is negligible (Overall: Neutral Salt - This solution will have a pH closest to 7) Al(NO3)3 : Al3+ is acidic but NO3- is negligible (Overall: Acidic Salt)
What is the half reaction at the cathode in the molten electrolysis of CdCl2? Cd2+ + 2e- → Cd Cd → Cd2+ 2e- Cl2 + 2e- → 2Cl- 2Cl- → Cl2 + 2e-
Cd2+ + 2e- → Cd since reduction happens at the cathode (RED CAT) choices B and D could be eliminated as they are oxidation half reactions (electrons on the product side are lost). In the molten electrolysis of a binary salt, the cation is reduced at the cathode to its elementary form: Cd2+ + 2e- → Cd and so answer choice A is correct.
which of the following has an ionic radius greater than its atomic radius K Mg Ag Cl
Cl anions are the result of gaining e- --> resulting greater ionic radius cations do the opp
Which of the following gases will have the lowest average velocity at 150 C? CO2 CH4 Ar Cl2
Cl2 A gas kinetic energy is a function of its temperature and since all these gases are at the same temperature (150 C) they will all have the same kinetic energy. (KE is proportional to temp) Since K.E. =1/2mv^2 , the gas with the largest mass (m) will have the lowest average velocity (v) and Cl2 has the largest mass of the choices listed.
Which of the following would increase the solubility of HCl(g) in water? Increasing the temperature and increasing the pressure Decreasing the temperature and increasing the pressure Increasing the temperature and decreasing the pressure Decreasing the temperature and decreasing the pressure
Decreasing the temperature and increasing the pressure Gases are more soluble in liquids at low temperatures and high pressures.
Which of the following is true about a galvanic cell? Electrons travel from cathode to anode through the salt bridge Electrons travel from anode to cathode through the salt bridge Electrons travel from anode to cathode through the wire Electrons travel from cathode to anode through the wire
Electrons travel from anode to cathode through the wire First, electrons travel through the wire whereas ions travel through the salt bridge and so choices A and B can be eliminated. Second, electrons always travel from anode to cathode in both galvanic and electrolytic cells and so choice C is correct and choice D is eliminated.
which of the following atoms are the heaviest Fe Fe2+ Fe- they r all the same
Fe-
Which of the following is a statement of the 2nd Law of Thermodynamics? The entropy of a system increases for a spontaneous process Energy cant be created or destroyed For a spontaneous process, ΔS universe > 0 Expanding gases cool
For a spontaneous process, ΔS universe > 0
which is the most polar bond H-F H-CL H-BR H-I
H-F most polar bond = greatest EN diff
Which of the following could be the pH at the equivalence point of the titration of HC2H3O2 with CsOH? 5.1 7.0 8.4 12.1
HC2H3O2 is a weak acid and CsOH is a strong base and the pH at the equivalence point of the titration of a weak acid with a strong base will be slightly basic, a pH between 7 and 10 being typical. Only 8.4 is in this range and is the correct answer.
how to find out the pKa looking at titration
In the titration of a weak acid with a strong base, pH = pKa at the half-equivalence point
Which of the following solutions is most basic? Pure water pOH=12 0.001M NH3 [H+]=1.0x10-11M
It is easiest to compare relative acidities and basicities based upon pH as this is what most of us are most familiar with. The most basic solution is the one with the highest pH. Pure water pH = 7 pOH = 12 so pH = 2 If NH3 were a strong base it would dissociate completely yielding [OH-] = 0.001M and so pOH = -log (0.001) = 3 and pH = 11. Since its a weak base we know the pH will be <11. [H+] = 1.0x10-11M so pH = -log (1.0x10-11M) = 11 which is the most basic of the choices.
which of the following has the highest 1st ionization energy B C N O
N
What are the products of molten electrolysis of NaCl? Na+ and Cl- Na+ and Cl2 Na and Cl2 Na and Cl-
Na and Cl2 In the molten electrolysis of a binary salt, the cation is reduced at the cathode to its elementary form. Na+ + e- --> Na In the molten electrolysis of a binary salt, the anion is oxidized at the anode to its elementary form. 2Cl- --> Cl2 + 2e- So the products are Na at the cathode and Cl2 at the anode and choice C is correct.
An aqueous solution of which of the following salts has a pH>7? KBr Na2SO4 CsI RbNO3
Na2SO4 This question test knowledge of the potential acidity/basicity of salts. Cations: Group 1 and 2 metal ions or metal ions with a +1 charge are negligible; all other cations are acidic. Anions: The general rule is the that conjugate base of a strong acid is a negligible base (Cl-, Br-, I-, NO3-, ClO4-, ClO3-) or an acid (in the case of HSO4-). But almost all other anions are basic. pH>7 means a basic solution and it is the anions that can act as bases so well focus on them. KBr Br- is negligible Na2SO4 SO42- isnt the conjugate base of a strong acid and is therefore basic CsI I- is negligible RbNO3 NO3- is negligible
Which of the following would behave most like an ideal gas? H2O Ne CO2 Xe
Ne In deciding which gas behaves the most ideally we should focus on which gas satisfies the following assumption of ideal gases the best: There are no attractive forces between molecules, i.e. all collisions are elastic. Therefore the gas with the lowest intermolecular forces can be expected to behave the most ideally. H2O has hydrogen bonding and can be expected to significantly deviate from ideal behavior. Ne, CO2, and Xe are all non-polar and therefore only have London dispersion forces. But as Ne is the smallest (lowest surface area) it will have the weakest London dispersion forces (and therefore lowest overall intermolecular forces) and will be expected to behave the most like an ideal gas.
What is the conjugate base of OH-? H2O O2- H3O+ H2O2
O2- This one is tricky. The question asks for the conjugate base of OH- so OH- must be the conjugate acid (which is why this is tricky as youve probably only ever seen OH- act as a base and a strong one at that). As the Bronsted-Lowry definition of an acid is a H+ (proton) donor, simply having OH- donate an H+ leads us the the conjugate base, O-2.
what does pressure affect? s, l, aq, g
ONLY gas
If the concentration of a 2nd order reactant is increased by a factor of 10, what will be the effect on the rate of the reaction? Rate doubles Rate increases by a factor of 5 Rate increases by a factor of 10 Rate increases by a factor of 100
Rate increases by a factor of 100 For a 2nd order reactant the rate depends upon the reactants concentration squared (Rate = k[A]^2). So if the reactant concentration is increase by a factor of 10, the rate will be increased by a factor of 10^2 or 100.
Which of the following is false about a voltaic cell? The cathode is negatively charged Cations travel to the cathode through the salt bridge Ecell > 0 Reduction occurs at the cathode
The cathode is negatively charged In a voltaic cell electrons travel spontaneously from the anode (which is negative) to the cathode (which is positive) and so choice A is the false statement. Incidentally, in an electrolytic cell electrons travel non-spontaneously from anode (which is positive)to cathode (which is negative). spontaneous = Ecell > 0
When Latex Formula is at 0 and is in a state of equilibrium at what level is the free energy in the system? The free energy is at its maximum equilibrium point The free energy is at a level consistent with the energy of the system The free energy is found within a specific range between 0-1 The free energy in the system is at a minimum
The free energy in the system is at a minimum The free energy in the system is at a minimum. Free energy is always looking to be at a minimum in the system. This means that it utilizes less energy and work is diminished on the system as well. That is why the number 0 for dG represents equilibrium because it is no longer changing, or in other words at its minimum energy point and therefore at equilibrium.
For a certain reaction ΔGstandard = -850kJ/mol. Which of the following statements is false concerning this reaction? This reaction is spontaneous under standard conditions At equilibrium, there will be more products present than reactants The equilibrium constant will be much smaller than 1 ΔHstandard - TΔSstandard < 0
With ΔGstandard < 0, this reaction is spontaneous under standard conditions ΔGstandard = -RTlnKeq shows the relationship between ΔGstandard and Keq. When ΔGst < 0, Keq > 1 and the reaction will favor the products. Since ΔGst= ΔHst- TΔSstand ΔGst < 0, then ΔHst-TΔSst < 0. As stated above, ΔGst= -RTlnKeq shows the relationship between ΔG° and Keq. When ΔGst < 0, Keq > 1 which implies that there will be more products than reactants present at equilibrium and not the other way around.
how to calculate ph,pOH given the Ka and concentration
[H+] = sqrt ( Ka x [HA]) same for OH
Which of the following can result in a change in the value of an equilibrium constant? A change in pressure A change in temperature Increasing the concentration of reactants Adding an inert gas
a change in temp A change in temperature is the only thing that can change the value of an equilibrium constant. A change in pressure and an increase in the concentration of the reactants can result in a shift in the equilibrium according to Le Chateliers Principle but do not change the value fo the equilibrium constant.
how to identify catalysts/ intermediates in a given equation
catalyst = reactant --> product intermediates : product first then reactant
Which of the following will increase the yield of H2? Mg2+(aq) + 2H+(aq) ↔ H2(g) + Mg(s) Decreasing the pH Removing Mg(s) Removing Mg2+(aq) Increasing the pressure
decreasing pH To increase the yield of H2, the reaction needs to shift right. Decreasing the pH (making the solution more acidic) increases the [H+], a reactant, therefore resulting in a shift to the right. Removing Mg(s) results in no shift as the addition/removal of solids dont shift an equilibrium as they dont show up in the equilibrium constant expression. Removing Mg2+ results in a shift left (as removing a reactant typically does). Increasing the pressure results in a shift left as it favors the side of the reaction with fewer moles of gas. Keep in mind that solids, liquids, and aqueous species are largely unaffected by a change in pressure. The reactants side has zero moles of gas while the products side has 1 mole of gas so the reactants side is indeed the side with fewer moles of gas.
Which of the following will increase the value of the equilibrium constant for the following reaction? CaCO3(s) ↔ CaO(s) CO2(g) ΔH = 178kJ Adding CaCO3 Removing CO2 Increasing the temperature Decreasing the temperature
increasing temp If the forward reaction is exothermic, increasing the temperature decreases the value of the equilibrium constant. If the forward reaction is endothermic, increasing the temperature increases the value of the equilibrium constant. This reaction has a positive enthalpy value so is endothermic.
When would the following reaction be expected to be spontaneous? 2NO(g) + O2(g) →N2O4(g) ΔH = -171 kJ low temperatures high temperatures all temperatures never
low temp First of all we must figure that ΔS < 0 as 3 mol gas → 1 mol gas. Plugging a negative ΔH and a negative ΔS into ΔG = ΔH - TΔS will yield a negative ΔG (ΔG<0 for a spontaneous rxn) only when T is small. Therefore the rxn is only spontaneous at low termperatures.
molarity =
mol / L
molatity
mol solute / Kg solvent
What was the concentration of the acid titrated in the titration curve below? name formula used how to find moles and volume
nAMAVA = nBMBVB nA is the number of acidic H+ ions the acid can donate and nB is the number of H+ ions the base can accept (typically equal to the number of OH- in the base). nB = 1 for NaOH nA = 1 as this is a monoprotic acid as there is only one equivalence point on the titration curve nAMAVA= nBMBVB (1)( MA)(10mL) = (1)(0.1M)(25mL) 25 mL is the volume at equivalence point MA = 0.25M
which of the following is parametic O2- Cl- Li+ None of these
none of these parametric - has unparied e or odd e
what is the equation to find delta H using deltaHf
pdts - reactants
in nuclear chem, are the reactants or pdts considered more stable
products bc they are now at a lower energy state, following the release of energy during radioactive decay
formula to calculate heat (q)
q = mc(deltaT)
what is the equation to find delta H using bond enthalpy
reactants - products
For which of the following phase changes is dH > 0 and dS > 0? freezing condensation sublimation deposition
sublimation (forward direction - dH > 0 and dS >0 ) freezing --> l to s condensation --> g to l sublimation --> s to g deposition --> g to s
When 0.1 moles of HCl is added to 1L of a solution containing 0.5M HCN and 0.5M NaCN, which of the following is true? The pH=1 The pH will increase a little The pH will increase a lot The pH will decrease a little
the pH will decrease a lil The 1L of solution containing 0.5M HCN and 0.5M NaCN is a buffer having a weak acid and the salt of its conjugate base. Buffers resist changes in pH. Therefore adding a little HCl (strong acid) will decrease the pH only a little, not a lot.
