y Institution Courses Community Conten Collection Service CHM 161 Combined FA18-
ID: 718015 • Letter: Y
Question
y Institution Courses Community Conten Collection Service CHM 161 Combined FA18-FA18 BlueDoorLabs CHM161 t 'observed" and "expected" value: Upon completing the lab, it was discoverd that the For the folilowing scenario, analyze balance used by one of your classmates for weighing the metal strip did not zero properly, consequently, all of their mass measurements are experimental (calculated) value of Avogardor's Number? the error and ies consequences, and explain answers clearly using the terms high by precisely 0 050g What effect will this have on therExplanation / Answer
If all the observed mass measurements are high by 0.050 g
Observed Mass of lost on anode will increase
Mass of atoms loss will decrease due to increase in mass of anode loss.
Expected value of Avogadro number will decrease due to low atoms in the metal.
Let's understand it by a Sample Calculation for each case
Case 1 - without any error
mass lost on anode = 0.3344 g
average current = 0.598 A
Time taken for the process = 1809 s
total charge passed = Average current x time
= 0.598 A x 1809 s x (1 Coulomb / 1A-s)
= 1081.78 Coulomb
Number of electrons = 1081.78 Coulomb x (1 electron / 1.602 x 10^-19 Coulomb)
= 6.753 x 10^21
Number of Cu2+ ions lost
= (6.753 x 10^21 electrons) x (1 Cu2+ / 2 electrons)
= 3.376 x 10^21
Mass of Cu2+ ions lost = (3.376 x 10^21 atoms) / (0.3344 g)
= 1.009 x 10^22 atoms/g
Calculated Avogadro number
= ( 1.009 x 10^22 atoms/g) x (63.546 g/mole)
= 6.416 x 10^23 atoms / mol
Case 2 - with an error of high 0.050 g measurement
mass lost on anode = 0.3344 + 0.050 = 0.3844 g
average current = 0.598 A
Time taken for the process = 1809 s
total charge passed = Average current x time
= 0.598 A x 1809 s x (1 Coulomb / 1A-s)
= 1081.78 Coulomb
Number of electrons = 1081.78 Coulomb x (1 electron / 1.602 x 10^-19 Coulomb)
= 6.753 x 10^21
Number of Cu2+ ions lost
= (6.753 x 10^21 electrons) x (1 Cu2+ / 2 electrons)
= 3.376 x 10^21
Mass of Cu2+ ions lost = (3.376 x 10^21 atoms) / (0.3844 g)
= 8.783 x 10^22 atoms/g
Calculated Avogadro number
= ( 8.783 x 10^22 atoms/g) x (63.546 g/mole)
= 5.581 x 10^24 atoms / mol
The calculated value of Avogadro number is decreased due to high measurement.
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