Chem 162 Final Exam
In the energy diagram below, the activation energy of the forward reaction is shown by which arrow?
bottom of curve to top of curve
A handheld device which measures radioactivity is called a Select one: a. spectrophotometer b. seismograph c. Geiger counter d. chromatograph e. mass spectrometer
c.
A reaction has a positive ΔH and a negative ΔS. The reaction will be Select one: a. Spontaneous at high T only b. Spontaneous at all T c. Nonspontaneous at all T d. Spontaneous at low T only
c.
Calculate E° for a reaction in which ΔG° = 5.09 x 104 J/mol and three electrons are transferred. F = 9.649 x 104 C/mol. Select one: a. None of these b. 0.175 V c. -0.175 V d. 1.47 x 1010 V e. -1.47 x 1010 V
c.
A Lewis base is a substance that Select one: a. Donates a proton b. Accepts a proton c. None of these d. Donates an electron pair e. Accepts an electron pair
d.
If the pOH of a solution is 9.0, what is the pH? Select one: a. 9.0 b. -9.0 c. 1.0 x 10-9 d. 5.0 e. None of these
d.
The equilibrium constant at a given temperature for the reaction H2(g) + Br2(g) ⇆ 2HBr(g) is 1.6 × 105. The value of K for the reverse reaction is Select one: a. 6.3 × 10-5 b. -1.6 × 105 c. 1.6 × 10-5 d. 6.3 × 10-6 e. 1.6 × 105
d.
For which of the following values of the equilibrium constant does the reaction at equilibrium give the highest concentration of products? Select one: a. 10-5 b. 10-3 c. 100 d. 103 e. 105
e.
If a nonvolatile solute is added to a solvent, you would expect the mixture to show a. Freezing point depression and boiling point elevation b. Freezing point elevation and boiling point depression c. None of these
a.
If a reaction consists of several steps, the rate-determining step is Select one: a. the slow step b. the step that gives off the most energy c. the first step d. the fast step e. the last step
a.
If a substance goes from a gas to a liquid, its entropy should Select one: a. Decrease b. Increase c. Remain the same
a.
If a weak acid has a Ka of 1.0 x 10-3, what is the Kb of its conjugate base? Select one: a. 1.0 x 10-11 b. None of these c. 1.0 x 10-17 d. 1.0 x 103 e. 1.0 x 10-3
a.
Which types of things could happen in a nuclear power plant? Select all that apply. Select one or more: a. A reactor core could melt down b. None of these c. A reactor core could become an atomic bomb d. A reactor core could explode and release radioactive substances
a. and d.
According to the Arrhenius equation, the rate constant k depends on temperature.
T
An elementary reaction is a reaction that occurs in a single step.
T
For the reaction 5A + B → 3C which fraction is equal to the rate?
-1/5(delta[A]/delta t)
Indicate how much of a substance is remaining after the indicated number of half-lives. after one half life: after two half lives:
1/2 1/4
A catalyst is used up in a chemical reaction.
F
What is the equilibrium constant expression for the following reaction: 4NH3(g) + 5O2(g) ⇄ 6H2O(g) + 4NO(g)
([H2O]^6[NO]4)/ ([NH3]^4[O2]^5)
Adding 17.5 g of an unknown compound to 100.0 g of water results in a freezing point lowering of -1.80 °C. Calculate the molality and molar mass of the unknown compound. You may assume that the density of water is 1.00 g/mL, and Kf for water is 1.86 °C/m. Equation: ΔTf = Kf m
0.9677m 1.81 g/mol
This question counts the weight of two questions. The reaction mechanism (containing elementary reactions) for the decomposition of H2O2 is H2O2 + I- → H2O + IO- slow step H2O2 + IO- → H2O + O2 + I- fast step Are the following statements true or false for the above reactions: 1. The second step is the rate-determining step. 2. the reaction can be approximated as first order with respect to [I-]. 3. In the two reactions above, what is the role of I-? 4. In the two reactions above, what is the role of the IO-?
1. F 2. T 3. Catalyst 4. Intermediate
Would each of the following be expected to affect the rate of a given chemical reaction? 1. The reaction temperature 2. The concentration of the reactants 3. A catalyst
1. Yes 2. Yes 3. Yes
1. A catalyst is a substance that increases the rate of a reaction without itself being consumed. 2. At equilibrium, the rates of the forward and reverse reactions are equal. 3. The equilibrium constant is represented by k and the rate constant is represented by K. 4. The equilibrium constant can change with a change in temperature. 5. The equilibrium constant can increase with the addition of a catalyst
1. t 2. t 3. f 4. t 5. f
For this problem you might want to use scrap paper. An acid HA has a value of Ka = 1.0 x 10-6. What is the pH of a 0.10 M solution of HA? Your answer should have the correct number of significant digits.
3.50
A buffer which is 0.20 M in HA and also 0.050 M in NaA has a pH of 4.44. What is the pKa? Your answer should have the correct number of significant digits.Possible equation to use:pH = pKa + log [base]/[acid]
5.04
For any reaction, the order of the reaction is given by the balancing coefficients.
F
The step that determines the rate of an overall reaction is the fast step.
F
What is the equilibrium constant expression for the following reaction: CoO(s) + H2(g) ⇆ Co(s) + H2O(g)
[H2O]/[H2]
Energy can be released by (select all that apply) Select one or more: a. Fissioning atoms heavier than iron apart to make lighter atoms b. Fissioning atoms lighter than iron apart to make even lighter atoms c. Fusing atoms lighter than iron together to make a heavier atom d. Fusing atoms heavier than iron together to make an even heavier atom
a and c
A basic solution contains no H3O+, and an acidic solution contains no OH-. Select one: a. False b. True
a.
A solution is prepared by dissolving 17.2 grams of ethylene glycol (molar mass 62.07 g/mol) in 0.500 kg of water. The final total volume of the solution is 515 mL. What is the molarity of ethylene glycol in the solution? Select one: a. 0.538 M b. 0.0334 M c. None of these d. 34.4 M e. 0.554 M f. 33.4 M
a.
A weak base is titrated with hydrochloric acid solution. At the equivalence point, Select one: a. pH < 7.0 b. pH > 7.0 c. pH = 7.0
a.
For the reaction S2-(aq) + I2(s) → SO42-(aq) + I-(aq) the final balanced reaction should be Select one: a. 4H2O(l) + S2-(aq) + 4I2(s) → SO42-(aq) + 8I-(aq) + 8H+(aq) b. None of these c. 2H2O(l) + S2-(aq) + 2I2(s) → SO42-(aq) + 4I-(aq) + 4H+(aq) d. 4H2O(l) + S2-(aq) + 2I2(s) → SO42-(aq) + 4I-(aq) + 8H+(aq) e. 4H2O(l) + S2-(aq) + I2(s) → SO42-(aq) + 2I-(aq) + 8H+(aq)
a.
How many significant figures are present in the following pH: pH = 10.95 Select one: a. Two b. Three c. One d. Four
a.
How should the addition of Ca2+ to a solution containing CaCO3 affect how much CaCO3(s) can dissolve? Select one: a. It should make it dissolve less CaCO3 b. It should not affect the amount that dissolves c. It should make it dissolve more CaCO3
a.
If HNO2 is a weak acid, its conjugate base is Select one: a. NO2- b. HNO- c. HNO3 d. H2NO2 e. None of these
a.
If Q > K for a reaction, this means that Select one: a. the reaction will go backwards to reach equilibrium b. the reaction is already at equilibrium c. the reaction will go forward to reach equilibrium
a.
If the following reaction is at equilibrium, what happens if we add more H2(g) to the following reaction: CoO(s) + H2(g) ⇄ Co(s) + H2O(g) Select one: a. The reaction shifts forward b. The reaction shifts backward c. No shift
a.
If the temperature of a reaction is increased, what usually happens to the rate and the rate constant k? Select one: a. rate increases and k increases b. rate decreases and k remains constant c. rate increases and k remains constant d. rate decreases and k decreases e. none of these
a.
If you were a researcher who discovered an overall reaction, how would you determine the order of the reaction? Select one: a. By conducting experiments b. By looking at the coefficients in the balanced reaction
a.
In a nuclear reactor, the purpose of the control rods is to (pick the best answer) Select one: a. Slow down the nuclear reaction by absorbing neutrons b. Speed up the nuclear reaction by emitting neutrons c. Speed up the nuclear reaction by absorbing neutrons d. None of these e. Slow down the nuclear reaction by emitting neutrons
a.
The effect of a catalyst on the activation energy of a reaction is to a. Lower the activation energy b. Raise the activation energy c. None of these
a.
The standard state, given by the degree sign, refers to Select one: a. A gas at 1 atm pressure or a solution at 1 M concentration b. A substance in its stablest state that has a ΔS°f of 0 c. A substance at 1 atm pressure and 25°C d. A substance in its stablest state that has a ΔG°f of 0
a.
Under which condition is a reaction spontaneous in the forward direction? Select one: a. ΔG negative and E positive b. ΔG positive and E negative c. ΔG negative and E negative d. None of these e. ΔG = 0 and E = 0
a.
What is the correct way to balance the following reaction?K+(aq) + Cr(s) → K(s) + Cr3+(aq) Select one: a. 3K+(aq) + Cr(s) → 3K(s) + Cr3+(aq) b. 2K+(aq) + Cr(s) → 2K(s) + Cr3+(aq) c. 2H+(aq) + K+(aq) + Cr(s) → K(s) + Cr3+(aq) + H2O(l) d. None of these e. K+(aq) + Cr(s) → K(s) + Cr3+(aq)
a.
When the temperature of a substance decreases, what happens to the entropy of the substance? Select one: a. It decreases b. It is unaffected by a temperature change c. It increases
a.
Which nucleus below should be most stable? (Magic numbers, which may or may not be used, are p, n: 2, 8, 20, 28, 50, 82; p: 114; n: 126.) Select one: a. 12753I b. 12653I
a.
Which of the following mixtures can make a buffer? Select one: a. HA (weak acid) and NaA b. HBr and NaBr
a.
Which of the following mixtures can make a buffer? Select one: a. NH3 and NH4Cl b. NaOH and NaCl
a.
Which of the following salts is more soluble? Select one: a. A salt with the larger Ksp b. A salt with the smallest Ksp
a.
Which of these pH values is the most acidic? Select one: a. pH = 0 b. pH = 14
a.
Which statement about mass and energy is correct? Select one: a. Mass can be converted into energy, and a very small amount of mass can give a large amount of energy. b. Mass can be converted into energy, but it takes a huge amount of mass to create a small amount of energy. c. Mass cannot be converted into energy because mass is conserved.
a.
Which substance would be the most soluble in a nonpolar solvent? Select one: a. N2 b. H2O c. NO
a.
Which type of cell has a spontaneous redox reaction and functions as a battery? Select one: a. Voltaic b. None of these c. Einsteinian d. Electrolytic
a.
Write the cell notation (with the vertical lines) for a reaction in which H+(aq) is reduced to H2(g) at a C(graphite) electrode, and a Pb(s) electrode is oxidized to Pb2+(aq). Select one: a. Pb(s) | Pb2+(aq) || H+(aq) | H2(g) | C(graphite) b. Pb(s) | Pb2+(aq) || H+(aq), H2(g) | C(graphite) c. C(graphite) | H2(g) | H+(aq) || Pb2+(aq) | Pb(s) d. Pb(s) | Pb2+(aq) || H+(aq) | H2(g) e. None of these
a.
You would expect a molecule of the formula C8H18 to be most soluble in Select one: a. C6H6 b. H2O c. NH3 d. None of these e. CH3OH
a.
You would expect a molecule of the formula C8H18 to be most soluble in a. C6H6 b. none c. H2O d. CH3OH e. NH3
a.
A California politician was making a correct statement when he said that we ought to get the pH of acid rain all the way down to zero. Select one: a. True b. False
b.
A colligative property is a property that (pick the best answer): Select one: a. Depends on both the identity of the solute and its concentration b. Depends on the concentration of the solute and not its identity c. Depends on the lattice energy and the energy of hydration d. Depends on the molality but not the molarity e. Depends on the identity of the solute and not its concentration
b.
A solution is prepared by dissolving 17.2 grams of ethylene glycol (molar mass 62.07 g/mol) in 0.500 kg of water. The final total volume of the solution is 515 mL. What is the molarity of ethylene glycol in the solution? Select one: a. 0.0334 M b. 0.538 M c. 33.4 M d. None of these e. 34.4 M f. 0.554 M
b.
For the ELEMENTARY reaction A + B → C + D, the rate law must be a. rate = k[B]2 b. rate = k[A][B] c. rate = k([A]+[B]) d. rate = k([C][D])/([A][B]) e. rate = k[A]2
b.
How does a catalyst make a reaction go faster? Select one: a. Raises the activation energy b. Lowers the activation energy
b.
How many neutrons are present in an atom of nitrogen-15? Select one: a. 5 b. 8 c. 14 d. 15 e. None of these f. 7
b.
If 0.100 mol of solute is added to 0.500 L of solvent with a density of 0.790 g/mL, the molality of the solution is a. 0.166 m b. 0.253 m c. 1.27x10^-4 m d. none e. 0.200 m
b.
If the H3O+ concentration of a solution is 5.0 x 10-12, what is the OH- concentration? Select one: a. 5.0 x 10-26 b. 2.0 x 10-3 c. 2 x 1025 d. None of these e. 5.0 x 102
b.
The maximum work that a reaction could do (if no energy were wasted as entropy) is given by Select one: a. None of these b. ΔG c. ΔU d. ΔH e. ΔS
b.
The reaction Zn(s) → Zn2+(aq) + 2e- is a(n) Select one: a. Neither b. Oxidation reaction c. Reduction reaction
b.
What is true about the relationship between entropy and the number of ways to obtain a given arrangement? Select one: a. The larger the number of ways (W) to obtain a given arrangement, the lower the entropy b. The larger the number of ways (W) to obtain a given arrangement, the greater the entropy c. The number of ways (W) to obtain a given state is independent of the entropy
b.
When the pH of a solution decreases by 1, the acidity is 10 times greater. Select one: a. False b. True
b.
Which nucleus below should be most stable? (Magic numbers, which may or may not be used, are p, n: 2, 8, 20, 28, 50, 82; p: 114; n: 126.) Select one: a. 3720Ca b. 3820Ca
b.
Which nucleus below should be most stable? (Magic numbers, which may or may not be used, are p, n: 2, 8, 20, 28, 50, 82; p: 114; n: 126.) Select one: a. 8638Sr b. 8838Sr
b.
Which nucleus must be radioactive? Select one: a. None of these b. Po (Z = 84) c. Hg (Z = 80) d. Pb (Z = 82)
b.
Which of the following elements is a transition element? Select one: a. Ca b. Co c. Ge d. Br e. None of these
b.
Would you expect the complex ion Fe(CN)64- to be water soluble? Select one: a. No b. Yes c. Can't tell
b.
Given the following reduction potentials, which is a better oxidizing agent? Ag+(aq) + e- → Ag(s) 0.80 V Ni2+(aq) + 2e- → Ni(s) -0.23 V Select one: a. Ni2+(aq) b. Ag(s) c. Ag+(aq) d. Ni(s)
c.
If the following reaction is at equilibrium, what happens if we add more CoO(s) to the following reaction: CoO(s) + H2(g) ⇄ Co(s) + H2O(g) Select one: a. The reaction shifts backward b. The reaction shifts forward c. No shift
c.
In the complex ion [Cu(H2O)6]2+, identify the ligand. Select one: a. [Cu(H2O)6]2+ b. There is no ligand c. H2O d. Cu2+
c.
This question counts the weight of two questions. Using the Nernst equation, calculate Ecell for the reaction Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s) when the concentration of Cu2+(aq) is 0.00100 M and the concentration of Zn2+ is 1.00 M at 25°C. E˚cell is 1.10 V. Choose from these possible equations: ΔG˚ = -RTlnK , OR E = E˚ - (0.0592/n) log Q Select one: a. 1.28 V b. 1.19 V c. 1.01 V d. 0.92 V e. None of these
c.
Using the cell potentials below, calculate the potential (V) for the following reaction: 2Ag(s) + Ni2+(aq) → 2Ag+(aq) + Ni(s) Cell potentials: Ag+(aq) + e- → Ag(s) 0.80 V Ni2+(aq) + 2e- → Ni(s) -0.23 V Select one: a. None of these b. 0.57 V c. -1.03 V d. 1.03 V e. -0.57 V
c.
Using the cell potentials below, in which direction will the following reaction be spontaneous under standard conditions? 2Ag(s) + Ni2+(aq) → 2Ag+(aq) + Ni(s) Cell potentials: Ag+(aq) + e- → Ag(s) 0.80 V Ni2+(aq) + 2e- → Ni(s) -0.23 V Select one: a. Spontaneous in neither direction b. Spontaneous in the forward direction c. Spontaneous in the reverse direction
c.
What is the most common charge for transition elements when they form ions? Select one: a. -3 b. -1 c. +2 d. +1 e. -2 f. +3
c.
What is true when a reaction is at equilibrium? Select one: a. ΔG is positive b. ΔG is negative c. ΔG = 0 d. ΔG° = 0 e. None of these
c.
What would you expect to happen to the boiling point of a liquid when a nonvolatile solute is added to it? Select one: a. Nothing b. Boiling point depression c. Boiling point elevation
c.
When balancing the following half-reaction, where should electrons be added? I2(s) → 2I-(aq) Select one: a. On the right of the arrow, with the I- b. Nowhere; the reaction doesn't need electrons c. On the left of the arrow, with the I2
c.
Which d orbitals are in the ground-state electron configurations of elements 21 through 30? Select one: a. 1d b. 2d c. 3d d. 4d e. None of these
c.
Which is the strongest acid of those shown below? Select one: a. All are of equal acid strength b. HOBr c. HOCl d. HOI
c.
Which of the following is a weak base? Select one: a. None of these b. Sr(OH)2 c. NH3 d. LiOH e. Ba(OH)2
c.
Which of the following is the Kb reaction for a weak base B? Select one: a. B + H3O+ produces BH+ + H2O b. B + OH- produces BOH c. B + H2O produces BH+ + OH-
c.
Which statement best reflects the second law of thermodynamics? Select one: a. A perfectly crystalline substance has an entropy of zero at absolute zero temperature b. The total enthalpy of a system always increases for a spontaneous process c. The total entropy of a system and its surroundings always increases for a spontaneous process d. The total entropy of a system always increases for a spontaneous process e. The total enthalpy of a system and its surroundings always increases for a spontaneous process
c.
Which substance would be the most soluble in a nonpolar solvent? Select one: a. H2O b. NO c. N2
c.
molality (m) is a. Moles solute per liter solvent b. Moles solute per liter solution c. Moles solute per kilogram solvent d. Moles solute per kilogram solution e. None of these
c.
At which electrode does reduction take place? Select one: a. Neither b. Anode c. Both d. Cathode
d.
For a reaction spontaneous in the forward direction, Select one: a. K < 1 b. K = 1 c. K = 0 d. K > 1
d.
For this problem you might want to use scrap paper. Calculate the solubility, in mol/L, of PbI2. Ksp = 6.5 x 10-9 For your benefit, please write out the Kspreaction on your scrap paper. Select one: a. 0.0019 b. None of these c. 0.0015 d. 8.1 x 10-5 e. 0.0012
d.
This question counts the weight of two questions. The equilibrium constant for a reaction with ΔG˚ = 50.0 kJ/mol at 25°C is (R = 8.314 J/(K mol)) Select one: a. None of these b. 1.09 x 109 c. 0.980 d. 1.72 x 10-9 e. 3.36 x 10-105
d.
What is the correct way to balance the following half-reaction:BrO3-(aq) → Br-(aq) Select one: a. 2BrO3-(aq) → 2Br-(aq) + 3O2(g) b. None of these c. 6H+(aq) + BrO3-(aq) → Br-(aq) + 3H2O(l) + 6e- d. 6H+(aq) + 6e- + BrO3-(aq) → Br-(aq) + 3H2O(l) e. BrO3-(aq) → Br-(aq) + 3O(g)
d.
Will a mixture containing 0.010 M magnesium (Mg2+) salt and 0.010 M oxalate (C2O42-) salt form a magnesium oxalate precipitate (MgC2O4Ksp = 8.5 x 10-5)? Select one: a. Yes, because Q < Ksp b. No, because Q > Ksp c. No, because Q < Ksp d. Yes, because Q > Ksp
d.
gases are most soluble in water at a. high temps and low pressures b. high temps and high pressures c. low temps and low pressures d. low temps and high pressures
d.
If a solution contains 30. ppm (parts per million) of a pollutant, what percentage is this? a. 3.0 x 10-4 percent b. 0.30 percent c. None of these d. 3.0 x 10-5 percent e. 0.0030 percent
e.
If a weak acid has a Ka of 1.0 x 10-3, what is the pKa? Select one: a. 1.0 x 10-11 b. -3.0 c. None of these d. 1.0 x 10-3 e. 3.0
e.
If the pH of a solution is 8.92, what is the H3O+concentration? Select one: a. 8.3 x 10-6 b. None of these c. 0.95 d. 8.3 x 108 e. 1.2 x 10-9
e.
The function of a salt bridge is to Select one: a. Prevent electrocution b. Donate electrons to the cathode to assist in reduction c. Donate electrons to the anode to assist in reduction d. Function as a sacrificial electrode to keep the battery from corroding e. Allow the flow of salt ions to prevent charge buildup
e.
The reaction below is endothermic: 5CO(g) + I2O5(g) ⇆ I2(g) + 5CO2(g) The yield of products could be increased by Select one: a. none of these b. decreasing the temperature c. decreasing the pressure d. increasing the pressure e. increasing the temperature
e.
Using scrap paper, finish balancing the following reaction in basic solution: 4H+(aq) + PbO2(s) + 2I-(aq) → Pb2+(aq) + I2(s) + 2H2O(l) Select one: a. 2H2O(l) + PbO2(s) + 2I-(aq) → Pb2+(aq) + I2(s) b. 4H2O(l) + PbO2(s) + 2I-(aq) → Pb2+(aq) + I2(s) + 2H2O(l) + 4OH-(aq) c. None of these d. 2H+(aq) + PbO2(s) + 2I-(aq) → Pb2+(aq) + I2(s) + 2OH-(aq) e. 2H2O(l) + PbO2(s) + 2I-(aq) → Pb2+(aq) + I2(s) + 4OH-(aq)
e.
What is the correct electron configuration for the V3+ ion? V (vanadium) is number 23 in the periodic table. Select one: a. [Ar]4s23d3 b. [Ar]4s24d3 c. [Ar]4s2 d. [Ar]4d2 e. [Ar]3d2 f. None of these g. [Ar]4s23d6
e.
What value of K would you expect for the reaction A ⇄ B if, after it has come to equilibrium, it produces very little product B and consists of mostly reactant A? (Hint: Think of the mathematical expression for K.) Select one: a. K would be a large negative number b. K would be zero c. K would be a very small negative number d. K would be a large positive number e. K would be a very small positive number
e.
Which of the following is a weak acid? Select one: a. All are strong acids b. HNO3 c. H2SO4 d. HI e. H2S
e.
Which set of equations is completely correct? Select one: a. ΔH˚ = -nFE˚ = -RTlnK = ΔG˚ - TΔS˚ b. ΔG = nFE = RTlnK = ΔH - TΔS c. ΔG˚ = nFE˚ = RTlnK = ΔH˚ - TΔS˚ d. None of these e. ΔG˚ = -nFE˚ = -RTlnK = ΔH˚ - TΔS˚
e.
the definition of molality (m) is a. mol solute per liter of solution b. none c. mol solute per liter of solvent d. mol solute per kilogram of solution e. mol solute per kilogram of solvent
e.
Choose the correct product for the reaction below: 21585At → ? + 42α Select one: a. 22389Ac b. 0-1e c. 21585At d. None of these e. 21987Fr f. 21183Bi
f.
This question counts the weight of two questions. Uranium-235 is an unstable isotope which decays to lead-207 with a half-life of 7.04 x 108 years. If scientists found that the fraction of U-235 that decayed to Pb-237 in a sample of rock was 37.1 percent (or 62.9 percent of the original U-235 was remaining), calculate the apparent age of the rock according to this data. Select one: a. 1.01 x 109 years b. None of these c. 4.56 x 10-10 years d. 4.43 x 108 years e. 4.21 x 109 years f. 4.71 x 108 years g. 2.61 x 108 years
f.
This question counts the weight of two questions. The half-life of a reactant in a first-order reaction was measured to be 6.10 hours. If the starting concentration is 1.00 M, what is the remaining concentration after 7.43 hours? The first-order rate equations are ln [A]t = -kt + ln [A]0 and t1/2=0.693/k Calculate k, the rate constant and select the correct units for k (leave one extra significant figure to prevent rounding error). Calculate the remaining concentration after 7.43 hours.
k=0.01136 1/hr 0.430 M
A student drinks a cup of coffee which gives an initial caffeine concentration of 15 mg/L in the bloodstream. Two hours later, the student takes a chemistry exam. The reaction of caffeine in the body is approximately first order, and the half-life of caffeine in the student's body is 6.0 hours. What is the remaining concentration of caffeine in the student's bloodstream after 2.0 hours?
k=0.1155/hr final concentration= 12 mg/L
Ten years from now in your ground-breaking research, you determine the rate constant k for a given reaction at four different temperatures. You wish to calculate the activation energy of the reaction. The best way to calculate Ea from your data, using the equation below, is ln k=(-Ea/R)(1/T)+ln A
plot ln k as y and 1/T as x, and get the slope
Select the correct expression for the rate of the following reaction, in terms of the concentrations of reactants and products. 2 H2O2 → 2 H2O + O2
rate= -1/2[H2O2]/d. t =1/2[h2o]/d.t =1/1[o2]/d. t
the rate law for a second-order reaction is written
rate=k[A]^2
If you are given the rate constant of a reaction at four different temperatures, how would you calculate the activation energy from the equation ln k= -Ea/RT+ln A plot what as x? plot what as why? activation energy calculated from?
x: 1/T y: ln k Ea: slope=-Ea/R