The bottom of the beaker is half-covered with 30-mesh zinc metal. (A) Two pennies are lying on top of the 30-mesh zinc.
(B) Two pennies are lying on the bottom of the beaker but not in contact with the 30-mesh zinc. (C) A penny soldered to copper wire is immersed in solution, the other end of the copper wire being soldered to a strip of zinc metal in contact with 30-mesh zinc on the bottom of the beaker. (D) A penny soldered to copper wire is immersed in solution. The solution in the beaker is 1 M NaOH.
Review the General Soldering Instructions in Part I. Place the freshly tinned tip of the penny next to the wire angling the iron to get good thermal contact. Don't dab at the joint with the tip of the iron while soldering.
When the solution has warmed, use forceps to place two copper pennies on top of the granular zinc metal and two pennies in the area that is free of granular zinc (make sure that the pennies on the uncovered side do not contact even one grain of zinc). Bend a small "foot" on the penny in the beaker as shown in Figure 5. The "foot" of the zinc strip should rest on the granular size so that both are in direct contact. The penny should be completely immersed in solution but should not contact any granular zinc metal on the bottom of the beaker. Finally, hang the last penny (the one with only copper wire soldered to it) over the edge of the beaker so that the penny is completely immersed in solution. See Figure 5.
HINT- use an empty 400-mL beaker to bend and shape your soldered metal pieces to match what is pictured in Figure 5. Do this before attempting to put them in the 400-mL beaker containing your warm NaOH solution.
30min.
Leave the pennies in the beaker until some of them turn a silvery color. This may take anywhere from 5 to 30 min., depending on the temperature of the solution. (Some of the pennies will never turn silver even after waiting an hour or more.)
Which pennies turn a silvery color? Is it the three pennies that are in contact with the solution and with zinc, either directly or through the copper wire? Or is it the three pennies in contact with the solution but not indirect or indirect contact with zinc metal? 5-10min.
Using a pair of forceps, remove the pennies that have turned a uniform silvery color, rinse them with water, and put the pennies on a hot plate for a few seconds. Watch what happens to the silver-colored pennies as they heat on the hot plate. Keep the solution warm in the beaker in case you need to repeat some part of the experiment or try some new experiment, as described below.
5-10min.
Further Experiments. Solder another length of copper wire to a shiny clean penny. Actually, you can use the lone penny soldered to the copper wire from the first part of the experiment, just clean it with steel wool and deionized water. Connect one lead of a voltmeter to a zinc strip and the other lead to the copper wire soldered to the penny. Using the same solution you prepared earlier, immerse the zinc strip and penny in the solution.
Is there a voltage difference between the zinc strip and the copper wire soldered to the copper penny? Which metal is the electron source (the negative terminal of this electrochemical cell)?5-10min.
Do you think a current flows in the copper wire connecting the zinc strip and copper penny when both are immersed in the solution? If so, which direction will electrons flow, and what are the anode and cathode reactions?
Put the digital voltmeter into its current measuring mode on its most sensitive (microampere) scale. Then see if any current is flowing when you connect the meter in series between the copper wire soldered to the penny and to the zinc strip -both the penny and the zinc strip should be immersed in the hot 1 M NaOH solution. The series connections should look like this: Penny/copper wire/(+) ammeter(-)/zinc strip.
How large a current flows? . Is the current (charge flow) from penny to zinc strip or vice versa?
In wires the charge carriers are electrons. Current (defined as a flow of positive charge) is opposite to the flow of electrons.
In which direction are electrons flowing: from penny to zinc strip or vice versa?
example of the calculation of molar mass:
Graph the electric current (in amps) on the y-axis against time (in seconds) on the x-axis. The total charge that passed through the electrolysis cell is given by the area beneath this curve. If the current is constant, this area is:
Calculate this charge in coulombs.
Convert the coulombs of charge to mol electrons:
N =
The equation for the reduction half-reaction responsible for the plating at the cathode is
Use the mol ratios of the preceding balanced equation to calculate the number of moles of Cu plated out:
Use the initial and final masses of the copper mesh electrode to calculate the mass of copper plated out:
m(Cu) = m(final) – m(initial)
Calculate the molar mass (M) of copper:
M =
Questions & Answers
A golfer on a fairway is 70 m away from the green, which sits below the level of the fairway by 20 m. If the golfer hits the ball at an angle of 40° with an initial speed of 20 m/s, how close to the green does she come?
A mouse of mass 200 g falls 100 m down a vertical mine shaft and lands at the bottom with a speed of 8.0 m/s. During its fall, how much work is done on the mouse by air resistance
Chemistry is a branch of science that deals with the study of matter,it composition,it structure and the changes it undergoes
Adjei
please, I'm a physics student and I need help in physics
Adjanou
chemistry could also be understood like the sexual attraction/repulsion of the male and female elements. the reaction varies depending on the energy differences of each given gender. + masculine -female.
Pedro
A ball is thrown straight up.it passes a 2.0m high window 7.50 m off the ground on it path up and takes 1.30 s to go past the window.what was the ball initial velocity
2. A sled plus passenger with total mass 50 kg is pulled 20 m across the snow (0.20) at constant velocity by a force directed 25° above the horizontal. Calculate (a) the work of the applied force, (b) the work of friction, and (c) the total work.
you have been hired as an espert witness in a court case involving an automobile accident. the accident involved car A of mass 1500kg which crashed into stationary car B of mass 1100kg. the driver of car A applied his brakes 15 m before he skidded and crashed into car B. after the collision, car A s
can someone explain to me, an ignorant high school student, why the trend of the graph doesn't follow the fact that the higher frequency a sound wave is, the more power it is, hence, making me think the phons output would follow this general trend?
Nevermind i just realied that the graph is the phons output for a person with normal hearing and not just the phons output of the sound waves power, I should read the entire thing next time
Joseph
Follow up question, does anyone know where I can find a graph that accuretly depicts the actual relative "power" output of sound over its frequency instead of just humans hearing
Joseph
"Generation of electrical energy from sound energy | IEEE Conference Publication | IEEE Xplore" ***ieeexplore.ieee.org/document/7150687?reload=true
A string is 3.00 m long with a mass of 5.00 g. The string is held taut with a tension of 500.00 N applied to the string. A pulse is sent down the string. How long does it take the pulse to travel the 3.00 m of the string?
