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A voltaic cell consists of Mn/Mn2+ and Pb/Pb2+ half cells. Calculate the concentration of Pb2+ when the concentration of Mn2+ is 1 M and Ecell is 0.44V.

Please help. I believe you use the equation Ecell = standard-Ecell - ( 0.0592V / n) (log Q), but I cannot get the right answer.

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(15.4 g / 18.0 g/mol) times 6.02 kJ/mol = 5.15 kJ = 5150 J

5150 J = (316 g) (?t) (4.184 J/g C)

?t = 3.90 C

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Home >All Categories > Science & Mathematics >Physics >Open Question Rampriya Member since:April 20, 2010Total points:292 (Level 2)I'm curious to know whether is there any formula for that !.i thought of considering a given bar magnet as a equivalent solenoid ,and find the magnetic field at a point near by?.In case of electrostatics.it is F=eE .But in this case how can i calculate the force on the iron piece.Please help and correct me if iam wrong.thanks :)Answer Question

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Home >All Categories > Science & Mathematics >Physics >Open Question VERTREX Member since:April 04, 2010Total points:113 (Level 1)In the design of a passenger bus, it is proposed to derive the motive power
from the energy stored in a flywheel. The flywheel, which has a moment of
inertia of 4.0 x 102 kgm2, is accelerated to its maximum rate of rotation of 3.0 x
103 revolutions per minute by electric motors at stations along the bus route.
a) Calculate the maximum kinetic energy that can be stored in the flywheel.
b) If, at an average speed of 36 kilometres per hour, the power required by the
bus is 20 kW, what will be the maximum possible distance between stations
on the level?Answer Question

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I know that Q=m(C)deltaT
. I just can't figure out how you set up the formula. I don't want you to give me the answer i just want help setting up the equation.

here's the info that i do know.

Q= 1950J
M=?
deltaT=33.8
C=.75(pyrex glass)

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2 ways

Newton

d = 0.5at^2
30m = 0.5 * 9.8 m/s^2 * t^2

4.9 t^2 = 30
t^2 = 6.122
t = 2.47 s

v= at = 9.8 m/s^2 * 2.47 s = 24.25 m/s

Energy

PE = KE

MGH = 0.5MV^2 (cancel M)

GH = 0.5V^2
9.8 * 30 = 0.5 V^2
294 = 0.5V^2
V^2 = 294/.5 = 588
V = 24.25 m/s

No matter how you do it, the answer is always the same. (It would be really bad if it was not!)

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"When 0.10g of magnesium ribbon was dissolved in an excess of dilute HCl, the temperature rose by 4.3 degrees C.A separate experiment showed that the same volume of acid required 500J to raise the temperature by 1.0 degree C."

From this I was able to work out the enthalpy change per mole of magnesium. The second part of the question is the bit I'm stuck on...

"In a similar experiment, solid magnesium carbonate reacted with an excess of dilute hydrochloric acid and the enthalpy change was found to be -90kJ mol^-1 of magnesium carbonate.

The enthalpy change of the formation of H2O is -285kJ mol^-1 and of CO2 is -393kJ mol^-1. Use this data and your result from above to calculate the enthalpy change of formation of MgCO3."

Can you please talk me through how to do it?

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Here is what it has:
a mixture that is 0.10 M in NaNO2 and 0.20 M in Ca(NO2)2
Ka of HNO2 = 4.5 x 10^-4

Please help!

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Home >All Categories > Science & Mathematics >Chemistry >Open Question somi Member since:March 24, 2011Total points:95 (Level 1)please show me how to do this problem.
Calculate the molarity of a sulfuric acid,H2SO4,solution if 25.1ml of 0.162M KOH is required to completely react with 24.6mL of the H2SO4 solution.
balanced equation- 2KOH + H2SO4 ---> 2 H2O + K2SO4Answer Question

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Home >All Categories > Science & Mathematics >Chemistry >Open Question Lisa Member since:December 25, 2010Total points:97 (Level 1)Some students did an investigation to determine the specific heat capacity of ice. They did this by heating 100g of water and 100 g of ice in separate beakers simultaneously on the same hot plate. The temperature of water changed from 22 degrees C to 24 degrees C while the temperature of ice changed from -7 degrees C to -3 degrees C. What is the specific heat capacity of ice if the specific heat capactiy of liquid water is 4.2 J/g/degrees C?Answer Question

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ds = v(dy² + dx²)

2ydy = 3x²dx
dy = (3x²/2y)dx
dy² = (9/4)(x^4/y^2)dx²
y^2 = x^3
dy² = (9/4)(x^4/x^3)dx²
dy² = (9/4)xdx²

ds = v[(9/4)x + 1]dx

ds = (1/2)v(9x+4) dx

ds = (dx/2)v(9x+4)

So, integrate ds over the interval of x where the arc is defined, and you'll have the arc length.

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