Rossero Bertolli | Firecracker experiment in beer bottle filled with water @rosserobertolli | Uploaded 13 years ago | Updated 9 hours ago
This is part two of an experiment I did for my study to be a science teacher.
part one: http://www.youtube.com/watch?v=5GZb2FmHlbE (empty bottle)
I did this experiment on my balcony, but I'v taken a lot of safety measures.
DO NOT TRY THIS YOURSELF!
it is seriously dangerous!
It's a normal sized firecracker in a water filled 33cl grolsch beer bottle.
Here are the calculations for the pressure in the bottle for a closed bottle
(assuming the reaction has taken place before the water can leave the bottle)
I'm assuming the firecracker contains aluminium-perchorate flash powder.
The reaction taking place is as following: 3 KClO4 + 8 Al → 4 Al2O3 + 3 KCl
I've measured that the firecracker contains 3 grams of flash powder.
The molecular mass of perchlorate is:
39,10+12,01+126,9+4*16,00 = 242,01 g/mol
The molecular mass of aluminium is:
26,98 g/mol
The molecular mass of 3 KClO4 + 8 Al is:
3*242,01+8*26,98 = 941,87 g/mol
The total amount of 3 KClO4 + 8 Al will be:
n = m/M
3,0/941,87 = 3,2E-3 mol 3 KClO4 + 8 Al
n*3 = 9,6E-3 mol perchlorate
n*8 = 25,6E-3 mol aluminium
9,6E-3+25,6E-3 = 35,2E-3 mol flash powder
Calculating the total amount of gas (n/11*8)
35,2E-3/11*8 = 25,6E-3 mol gas
The pressure inside the bottle:
Assuming the water can't be compressed the gas can only be compressed in the small pocket created by the firecracker itself. The volume of the firecracker is:
6,2π0,6^2 = 7,01cm^3
The pressure inside this volume will be:
p = n*R*T/V
p = 25,6E-3*8,3145*293/7,01E-6 = 89,0E5 Pa
Pa is in N/m^2. The water will transmit the force from a small surface (outside of firecracker) to a large surface (inside of beer bottle).
The outside surface of the firecracker is 25.6cm^2
The inside surface of the beer bottle is 296,9cm^2 (did my math)
The pressure on the bottle will be:
89,0E5/296,9*25,6 = 7,67E5 Pa
This is allmost 8 bar, the bottles have to withstand (at least) 5 bar
This is why the bottle explodes in pieces.
Watch my previous video for the same experiment, but this time with an empty bottle! Will it break too?
previous video:
http://www.youtube.com/watch?v=5GZb2FmHlbE
This is part two of an experiment I did for my study to be a science teacher.
part one: http://www.youtube.com/watch?v=5GZb2FmHlbE (empty bottle)
I did this experiment on my balcony, but I'v taken a lot of safety measures.
DO NOT TRY THIS YOURSELF!
it is seriously dangerous!
It's a normal sized firecracker in a water filled 33cl grolsch beer bottle.
Here are the calculations for the pressure in the bottle for a closed bottle
(assuming the reaction has taken place before the water can leave the bottle)
I'm assuming the firecracker contains aluminium-perchorate flash powder.
The reaction taking place is as following: 3 KClO4 + 8 Al → 4 Al2O3 + 3 KCl
I've measured that the firecracker contains 3 grams of flash powder.
The molecular mass of perchlorate is:
39,10+12,01+126,9+4*16,00 = 242,01 g/mol
The molecular mass of aluminium is:
26,98 g/mol
The molecular mass of 3 KClO4 + 8 Al is:
3*242,01+8*26,98 = 941,87 g/mol
The total amount of 3 KClO4 + 8 Al will be:
n = m/M
3,0/941,87 = 3,2E-3 mol 3 KClO4 + 8 Al
n*3 = 9,6E-3 mol perchlorate
n*8 = 25,6E-3 mol aluminium
9,6E-3+25,6E-3 = 35,2E-3 mol flash powder
Calculating the total amount of gas (n/11*8)
35,2E-3/11*8 = 25,6E-3 mol gas
The pressure inside the bottle:
Assuming the water can't be compressed the gas can only be compressed in the small pocket created by the firecracker itself. The volume of the firecracker is:
6,2π0,6^2 = 7,01cm^3
The pressure inside this volume will be:
p = n*R*T/V
p = 25,6E-3*8,3145*293/7,01E-6 = 89,0E5 Pa
Pa is in N/m^2. The water will transmit the force from a small surface (outside of firecracker) to a large surface (inside of beer bottle).
The outside surface of the firecracker is 25.6cm^2
The inside surface of the beer bottle is 296,9cm^2 (did my math)
The pressure on the bottle will be:
89,0E5/296,9*25,6 = 7,67E5 Pa
This is allmost 8 bar, the bottles have to withstand (at least) 5 bar
This is why the bottle explodes in pieces.
Watch my previous video for the same experiment, but this time with an empty bottle! Will it break too?
previous video:
http://www.youtube.com/watch?v=5GZb2FmHlbE
