1. If a current of 50 mA flows in a wire for 10 minutes, how many electrons pass
ID: 2141624 • Letter: 1
Question
1. If a current of 50 mA flows in a wire for 10 minutes, how many electrons passed through any cross section of the wire? Give your answer to 2 significant figures.
2. Suppose that the volume of hydrogen gas at STP (i.e., the temperature is 0 ?C and the partial pressure of H2 is 1 atm) collected at the cathode in an electrolysis experiment is 8 mL. How many moles of hydrogen does this correspond to? How many molecules of hydrogen gas have been collected? How many electrons contributed to the electrolytic current?
3. Use the Ideal Gas law to calculate the volume in L of 1.00 mol of an ideal gas at STP.
4. Suppose you accidentally stop your reaction too early or late so that the level of the liquid inside the hydrogen tube is 1.0 cm higher or lower than the water level in the tank. By what percentage will the gas pressure inside the tube be different from atmospheric pressure? (Hint: The pressure at depth h in a liquid of density (P) equals atmospheric pressure plus Pgh. Recall that the density of water is 1.0 g/cm^3 = 1000 kg/m^3.) This is very nearly equal to the percent error that this will contribute to the experimental value of ( e ) . You should find a small answer, indicating that it doesn
Explanation / Answer
1)Total charge flown = i*t=0.05 * 10 * 60 =30 c
electronic charge = 1.6 * 10^-19 c
so number of electrons =1.875 * 10^20
2)1 mole at STP occupies 22.4L volume
so 8ml cooresponds to 3.57 * 10^-4 moles
1 mole has 6.023 * 10^23 molecules
so total number of molecules = 2.15 * 10^20
number of electrons per molecule =2
total electrons contributed are 4.3 * 10 ^ 20
3) R=0.0821 ATm L/K mol
so V=RT/P
=0.0821 * 273/1
=22.4L
4)
Assuming e means atmospheric pressure
Pressure applied by hydrogen = 1000 * 10 * 0.01 Pa =100 Pa =0.001 Atm
so error value will be 0.1 % which can be neglagable for atmospheric pressure
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