2

(a) ΔrG° for the following reaction at 398 K is 2.6 kJ mol−1:

H2(g) + I2(g) → 2 HI(g)

If a gas mixture containing: 2.00 bar of H2, 2.00 bar of iodine vapour, and 0.500 bar of hydrogen iodide, is sealed in a container at 398 K, is the reaction at equilibrium? [4]

(b) Sketch a graph to show how the conductivity of a solution varies with concentration depending on whether the solute is a strong or weak electrolyte. Include the equation which allows the limiting molar conductivity to be obtained from the graph.

Explain why the graphs are different. [4]

The following questions are concerned with electrochemical cells.

(c) If I2 and Br2 are added to a solution containing I– and Br– , what reaction will occur if the concentration of each species is 1M? Explain your answer. The standard reduction potentials of iodine and bromine are given below:

I2 + 2 e– → 2 I– E° = +0.54 V

Br2 + 2 e– → 2 Br– E° = +1.09 V [4]

(d)

Cu(s) | Cu2+(aq, 0.1 mol dm–3 ) || Ag+ (aq, 1.0 mol dm–3 ) | Ag(s)

Ag+ (aq) + e– → Ag(s) E° = +0.80 V

Cu2+(aq) + 2 e– → Cu(s) E° = +0.34 V

(i) Calculate E°cell under standard conditions. [2]

(ii) Calculate Ecell for the concentrations given in the cell diagram above. [4]

(iii) Calculate ΔG for the above cell. [2]

In this problem you will determine the amount of force a rider needs to exert on a bicycle pedal to accelerate at a rate of 1.0 m/s^2.

(c) Now consider the system consisting of the rear wheel. The system includes the sprocket (gear wheel) attached to it. Assume that the rear sprocket has a radius of 2.5 cm and neglible mass compared to the wheel. Assume that the rear wheel has the same mass, radius, and moment of inertia as the front wheel. The sprocket is driven by the bicycle chain. Assume that the tension in the upper portion of the bicycle chain is nonzero, neglect the tension in the lower portion of the chain. Write a free-body diagram for the system. By considering the torques on the system, find the tension in the chain.

(d) Now consider the system consisting of the crank, which means the front sprocket, and the pedals. The system is mounted on a frictionless axle. Assume that the pedals are a distance of 17 cm from the crack axle, that the front sprocket has a radius of 8.0 cm. Assume that the entire crank assembly has a moment of inertia 2.5 x 10^-2 kg m^2. Assume that the bike pedals are oriented horizontally, and that the rider is pushing straight downward on the forward pedal with a force F, with no force on the back pedal. Write a free-body diagram for the system. By considering the torques on the system, find the force F. Does your answer change if we neglect the moment of inertia of the crank?

(e) Is this a realistic force for a rider to exert on a bike pedal? If not, estimate the maximum acceleration you think is realistic for a bicycle.

1. Given the following information

   Ag⁺(aq) + e^- ↔ Ag(s)   Eº_red = 0.799 V

   Ag₂CrO₄(s) + 2e^- ↔ 2Ag(s) + CrO₄^2-(aq) Eº_red = 0.450 V

   Determine the equilibrium constant at 25 °C for the reaction below:

   Ag₂CrO₄(s) ↔ 2Ag⁺(aq) + CrO₄^2-(aq)

   	1.	9 × 10-18
   	2.	1.6 × 10-12
   	3.	1.2 × 10-6
   	4.	1.6 × 1015
   	5.	1.7 × 1039

1. Examine the following half reactions and select the strongest oxidizing agent among the species listed.

   Cr²⁺(aq) + 2e^- ↔ Cr(s) Eº_red = -0.913 V

   Sr²⁺(aq) + 2e^- ↔ Sr(s) Eº_red = -2.89 V

   Fe²⁺(aq) + 2e^- ↔ Fe(s) Eº_red = -0.447 V

   Co²⁺(aq) + 2e^- ↔ Co(s) Eº_red = -0.28 V

   	1.	Cr2+(aq)
   	2.	Fe(s)
   	3.	Fe2+(aq)
   	4.	Sr2+(aq)
   	5.	Co2+(aq)

2 points   

QUESTION 5

1. Which of the changes below will increase the voltage of the following cell?

   Co | Co²⁺ (0.010M) || H⁺ (0.010 M) | H₂(0.50 atm) | Pt

   	1.	Increase the pressure of H2 from 0.50 atm to 1.0 atm
   	2.	Increase the concentration of H+ from 0.010 to 0.050 M.
   	3.	Increase the mass of Co electrode from 12 grams to 15 g.
   	4.	Increase the concentration of Co2+ from 0.010 M to 0.40 M.

Molar Mass Determination by Depression of the Freezing Point

A student determines the freezing point of a solution of 0.630 g of mandelic acid in 20.78 g of tbutanol. He obtains the following temperature-time readings:

Plot these data using any spreadsheet or plotting program. Note that the first several points fall roughly on a straight line. The last several points fall on a different straight line. Perform linear regressions on these two lines to determine the freezing point of the solution (the temperature at which the lines intersect is the freezing point of the solution). Ignore the rather substantial supercooling that occurred. Attach a copy of the plot to this sheet.

What is the freezing point of the solution?

What is the freezing point depression, ÄTf ? (Tf = 24.5C for t-butanol.)

What is the molality, m, of the mandelic acid in the solution? (Use Equation 1.3, Kf = 8.09 C/m.)

What is the molar mass of mandelic acid? Use Equation 5.4 as rearranged below:

____________C

____________C

____________ m

_________ g/mol

5. The molecular formula of mandelic acid is C8H8O3. Is the result you obtained in Part e consistent with this formula?

11- The pH of a sodium acetate-acetic acid buffer is 4.70. Calculate the ratio [CH3COO−] / [CH3COOH].






1- Calculate the pH of a 0.20 M NH3/0.20 M NH4Cl buffer after the addition of 25.0 mL of 0.10 M HCl to 65.0 mL of the buffer.


A- Enter your answer in the provided box.

A 21.0−mL solution of 0.110 M CH3COOH is titrated with a 0.240 M KOH solution. Calculate the pH after the following additions of the KOH solution:

(a) 0.00 mL
=_____


(b) 5.00 mL
=_______


C- Enter your answer in the provided box.

In a titration experiment, 21.9 mL of 0.813 M HCOOH neutralizes 24.4 mL of Ba(OH)2. What is the concentration of the Ba(OH)2 solution?
_____M

D- a) Calculate the pH of the 0.39 M NH3/ 0.73 M NH4Cl buffer system.

pH =


(b) What is the pH after the addition of 20.0 mL of 0.075 M NaOH to 80.0 mL of the buffer solution?

pH =



E- What mole ratio would you need to prepare a liter of "carbonate buffer" at a pH of 9.96?


______: 1.0 : 0

A) NaHCO3 : H2CO3 : Na2CO3
B) Na2CO3 : NaHCO3 : H2CO3

Choose the order of the compounds that is represented in the numeric ratio.



F- Enter your answer in the provided box.

The pH of a bicarbonate-carbonic acid buffer is 6.18. Calculate the ratio of the concentration of carbonic acid (H2CO3) to that of the bicarbonate ion (HCO3−).
(Ka1 of carbonic acid is 4.2 × 10−7.)

[H2CO3]
[HCO3−]
=

As your spaceship coasts toward Mars, you need to move a heavy load of 1200 kg along a hallway of the spacecraft that has a 90 degree right turn, without touching the walls, floor, or ceiling, by working remotely, using devices attached to the load that can be programmmed to fire blasts of compressed air for up to 1.0 s in any desired direction. During a blast the load is subjected to a force of 20 N. The center of the load must move 2 m along the first section of the hallway, starting at rest. Let the starting point be <0,0,0> m, with the first section ending at <4,3,0> m. Using just three blasts of compressed air, choose the times when these blasts should be scheduled, their durations, and their directions. How long does it take to complete the entire move?

I know it is not 24 s a similiar or the same question was post at another time and it is wrong. I came up with 13 minutes roughly. If you could be do your best to answer this question, the question is from matter & interactions 4th edition modern mechanics chapter 2. This question was within the usage of the momentum principle section and although you need a grasp of this principle a d = \v\ * t can be used to calculate it I believe. I used a small window of acceleration of 0.5s and a total of 1.0s acceleration at the turn two positions .5s each one ending another starting to get the one blast necessary then .5 seconds of deacceleration at the 4m interval end.  

Hope someone really answer this thank you.

By studying seismic measurements and geological evidence, scientists have made the following obser
vations about earthquakes. i. Small tremors (magnitude below 1.0 on the Richter scale) are almost constantly oc
curing on every continent.
ii. The number of earthquakes with magnitude at least 3.0 on the Richter scale averages
200,000 per year, worldwide.
iii. Based on geological evidence, the number of major earthquakes (magnitude> 7.0 on
the Richter scale) has averaged 20 per year, and this average rate has not changed over
the last 10,000 years.
iv. The number of earthquakes occurring each year is independent of the number that
occurred in any previous year.
v. The magnitude of an earthquake is inversely proportional to the logarithm of the
frequency that earthquakes of at least that magnitude occur. In other words, let
X(m) denote the expected number of earthquakes per year with magnitude greater
than or equal to m. Then logX(m) is proportional to m.
(a) Explain why it is reasonable to use a Poisson random variable to model the number of major
earthquakes occurring in any given period of time? Indicate which of the above observations
support your explaination.
(b) Let N(t) be a Poisson random variable that models the number of major earthquakes (magnitude
> 7.0) that will occur in the next t years. Give the probability mass function for N(t).
(c) Calculate the expected value and standard deviation for N(3).
(d) Calculate the probability that there will be at least 3 earthquakes in the next month.

You plan to invest in the Kish Hedge Fund, which has total capital of $500 million invested in five stocks:

Kish's beta coefficient can be found as a weighted average of its stocks' betas. The risk-free rate is 5%, and you believe the following probability distribution for future market returns is realistic:

1. What is the equation for the Security Market Line (SML)? (Hint: First determine the expected market return.)
   1. r_i = 3.7% + (7.3%)b_i
   2. r_i = 5.0% + (6.9%)b_i
   3. r_i = 4.0% + (8.1%)b_i
   4. r_i = 4.0% + (6.9%)b_i
   5. r_i = 5.0% + (8.1%)b_i

   -Select-IIIIIIIVV

2. Calculate Kish's required rate of return. Do not round intermediate calculations. Round your answer to two decimal places.

   %

3. Suppose Rick Kish, the president, receives a proposal from a company seeking new capital. The amount needed to take a position in the stock is $50 million, it has an expected return of 14%, and its estimated beta is 1.5. Should Kish invest in the new company?

   The new stock -Select-should notshould be purchased.

   At what expected rate of return should Kish be indifferent to purchasing the stock? Round your answer to two decimal places.

   %

5. Today Van de Graaff accelerators sometimes serve as “injectors” for other types of accelerators that then further increase the energy of the particles. Consider a Van de Graaff accelerator that is being used to accelerate protons. The high voltage terminal (metal sphere) of the Van de Graff is charged using a rubberized belt that is 30 cm wide and travels at a velocity of 20 m/s. Charge is sprayed onto the belt near the roller at the low voltage end and removed from the belt near the upper roller inside the high voltage terminal. The belt is given sufficient surface charge density at the lower roller to cause an electric field of 1.0 MV/m (i.e. approaching the breakdown field of air at atmospheric pressure which is ~ 3 MV/m) on each side of the belt. (a) What is the charging current delivered to the high voltage terminal in µA? Suppose we would like to accelerate the protons to an energy of 3 MeV. Take the radius of the spherical high voltage terminal to be the such that the electric field at the surface of the sphere just below the breakdown field of air (b) How long does it take to charge the high voltage terminal of the Van de Graaff from zero volts to 3 MV? The beam of 3 MeV protons is focused onto a lithium target. The beam is equivalent to a current of 5 µA. (c) At what rate do protons strike the target? (d) At what rate is energy (heat) produced in the target? (e) Would you consider the Van de Graaff a ‘source of emf ? Why or why not?

Iconic memory is a type of memory that holds visual information for about half a second (0.5 seconds). To demonstrate this type of memory, participants were shown three rows of four letters for 50 milliseconds. They were then asked to recall as many letters as possible, with a 0-, 0.5-, or 1.0-second delay before responding. Researchers hypothesized that longer delays would result in poorer recall. The number of letters correctly recalled is given in the table.

Delay Before Recall

0 0.5 1

5 5 5

10 6   2

7 9 6

6 3 4

10 5 2

10 8 5

(a) Complete the F-table. (Round your values for MS and F to two decimal places.)

Source of Variation SS    df MS F

Between groups ____. ____. ____. ___

Within groups (error) ____. _____. ____

Total _____. _____

(b) Compute Tukey's HSD post hoc test and interpret the results. (Assume alpha equal to 0.05. Round your answer to two decimal places.)

The critical value is for each _______. pairwise comparison.

Which of the comparisons had significant differences? (Select all that apply.)

___ Recall following no delay was significantly different from recall following a half second delay.

____Recall following no delay was significantly different from recall following a one second delay.

_____Recall following a half second delay was significantly different from recall following a one second delay.

______The null hypothesis of no difference should be retained because none of the pairwise comparisons demonstrate a significant difference.