Question

c. If a piece of jewelry were electroplated with gold for 25 seconds at 1.5 A, how many grams of gold would be plated?
(Note: 1 A = 6.241 1018 e–/s. The reaction for the reduction of gold ions to gold metal is Au+ + 1e– Au(s).) (1 point)

Answer 1

Reaction is
Au+ + 1e– -> Au(s)

Figure out how many electrons are put into the reaction in 25 seconds at 1.5 A, this will equal the amount of Au(s) atoms you produce

from atoms using avagadros number you can find moles from moles you can find grams

Answer 2

Any questions?

Answer 3

If you are having trouble with the math let me know I can help you through it

Answer 4

here's what i have so far.. 1 A = 6.241 1018 e–/s so….
1.5(6.241 x 1018 e-/s)25s = number of atoms reduced
number of atoms reduced = 2.34 E 20

Answer 5

so do i multiply that by avogrado's number(6.0221413e+23)

Answer 6

so 2.34 E 20*6.0221413e+23)

Answer 7

1.4091811e+24 moles right?

Answer 8

no wait i did this wrong

Answer 9

http://www.wolframalpha.com/input/?i=1.5%286.241+x+10^18+e-%2Fs%2925

Yeah you messed up the first calculation

Answer 10

i did plug that into my calculator but i must've misread something

Answer 11

number of atoms reduced 6.362*10^20

Answer 12

yep i got that

Answer 13

and then multiply by avogadro's #?

Answer 14

dont i need to find the mass of gold?

Answer 15

Yes but if you multiply you are going to get an absurd number, Avogadro's number has units,
6.022141*10^23 atom/mol

Answer 16

you will end up with atom^2/mol which is not useful

Answer 17

as units

Answer 18

1.4091811e+24 moles is 3.8*mass of the moon lol that is a lot of gold

Answer 19

oh wow yea haha

Answer 20

always pay attention to number sizes in chemistry and really any science

Answer 21

i realized i multiplied by 1018 instead of 10^18 it was a typo

Answer 22

Au+ + 1e– has to be used next...?

Answer 23

not really a big deal you can tell the number was in scientific notation

Answer 24

well it is a 1 to 1 reaction thus the number of electrons reacted = number of Au(s) produced

Answer 25

so you can just say that the number of electrons = number of atoms of Au(s) produced

Answer 26

i think my teacher said we have to convert this to moles and then grams.

Answer 27

yes you convert to moles using avagadros number

Answer 28

i know that for grams it's : mol of substance x (Atomic mass of substance/ 1 mol)

Answer 29

oh so i have to use avogadros #

Answer 30

so from above, we know that there are 6.362x10^20 atoms reduced. so i multiply this by avogadro's number right?

Answer 31

well look at the units of your two numbers
avagadros number:
6.022141*10^23 atom/mol

number of Au(s) atoms:
6.362*10^20 atom

you need to set these numbers up so you end up with just the units mole, remember just like numbers units can cancel out when divded and can be raised to powers when multiplied together

Answer 32

oh okay i got it!

Answer 33

so its 1.056434912x10^-3

Answer 34

moles*