Question:
Electrochemistry Problem Help!?
I didnt really understand this problem in my Lab sheet. If u could help me i would greatly appreciate it!A current of .5 a passes through a cell for 30 mins. a) how many coulombs of charge have passed through the cell?b) If this electrolysis deposits copper from a copper (II) solution, what mass of cooper will plate out?Thanks so much!
Answer:
I scuff them on a bench grinder with a wire wheel. Then clean them with brake cleaner. You can use a wire brush or course sand paper. You don't want the pads to be glazed - that's what fine sand paper will do to them. If you sand a piece of wood with fine sand paper, it will smooth it out.
You need to replace them. When brakes become glazed there's no fix other than replacement. And if they're getting glazed, you're using them too harshly. If that's the way that you ride, replace them with high-performance Kevlar, metallic, or ceramic pads. And don't forget to turn or replace the disks as well.
Our equation is: Al (3+) + 3e- --- Al 0.34 g / (27 g/mol) 0.0126 mol Al 0.0126 mol Al * (3 mol e- / a million mol Al) 0.0378 mol e- are required. 0.0378 mol e- * (6.022 * 10^23 electrons/mole) 2.275 * 10^22 electrons The cost of an electron is: a million.602 * 10^-19 C 2.275 * 10^22 electrons * (a million.602 * 10^-19 C/electron) 3645 C 3600 C
Our equation is: Al (3+) + 3e- --- Al 0.34 g / (27 g/mol) 0.0126 mol Al 0.0126 mol Al * (3 mol e- / a million mol Al) 0.0378 mol e- are required. 0.0378 mol e- * (6.022 * 10^23 electrons/mole) 2.275 * 10^22 electrons The value of an electron is: a million.602 * 10^-19 C 2.275 * 10^22 electrons * (a million.602 * 10^-19 C/electron) 3645 C 3600 C
a) A coulomb is defined as the amount of charge that 1A transfers in 1 second [1]. Therefore over 30 minutes you have 30*60 1800 seconds with a 0.5 A current this would yield 900 C of charge. b) 900C of charge relates to 900 * 6.24 * 10^18 [1] electrons or 5.616 * 10^21 electrons. The reaction Cu^2+ +2e^- -- Cu(s) uses 2 electrons for every copper atom deposited. Therefore the number of copper atoms deposited will be approximately 2.8*10^21 atoms or dividing this by avagado's number (6.022 * 10^23) yields 0.00466 mole. Given the atomic weight of copper is 63.546 g/ mol [2] the mass will be 0.00466 * 63.546 0.296 g Enjoy :)
I scuff them on a bench grinder with a wire wheel. Then clean them with brake cleaner. You can use a wire brush or course sand paper. You don't want the pads to be glazed - that's what fine sand paper will do to them. If you sand a piece of wood with fine sand paper, it will smooth it out.
You need to replace them. When brakes become glazed there's no fix other than replacement. And if they're getting glazed, you're using them too harshly. If that's the way that you ride, replace them with high-performance Kevlar, metallic, or ceramic pads. And don't forget to turn or replace the disks as well.
Our equation is: Al (3+) + 3e- --- Al 0.34 g / (27 g/mol) 0.0126 mol Al 0.0126 mol Al * (3 mol e- / a million mol Al) 0.0378 mol e- are required. 0.0378 mol e- * (6.022 * 10^23 electrons/mole) 2.275 * 10^22 electrons The cost of an electron is: a million.602 * 10^-19 C 2.275 * 10^22 electrons * (a million.602 * 10^-19 C/electron) 3645 C 3600 C
Our equation is: Al (3+) + 3e- --- Al 0.34 g / (27 g/mol) 0.0126 mol Al 0.0126 mol Al * (3 mol e- / a million mol Al) 0.0378 mol e- are required. 0.0378 mol e- * (6.022 * 10^23 electrons/mole) 2.275 * 10^22 electrons The value of an electron is: a million.602 * 10^-19 C 2.275 * 10^22 electrons * (a million.602 * 10^-19 C/electron) 3645 C 3600 C
a) A coulomb is defined as the amount of charge that 1A transfers in 1 second [1]. Therefore over 30 minutes you have 30*60 1800 seconds with a 0.5 A current this would yield 900 C of charge. b) 900C of charge relates to 900 * 6.24 * 10^18 [1] electrons or 5.616 * 10^21 electrons. The reaction Cu^2+ +2e^- -- Cu(s) uses 2 electrons for every copper atom deposited. Therefore the number of copper atoms deposited will be approximately 2.8*10^21 atoms or dividing this by avagado's number (6.022 * 10^23) yields 0.00466 mole. Given the atomic weight of copper is 63.546 g/ mol [2] the mass will be 0.00466 * 63.546 0.296 g Enjoy :)
