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Physics, Chemistry and Biology: Post your doubts here!

Iridescent

Iridescent

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Maro ashroof said:
assalamu alaykom...
chemistry question:
can someone please explain for me how does a voltaic cell work and what are the differences between sacrificial protection and cathodic protection?
Thank you in advance:)
Click to expand...

Voltaic cell: It changes chemical energy into electrical energy. It works by the difference between the reactivity of two metals. The more reactive metal is made the anode which is connected to the negative terminal of the volt meter. The flow of electrons in the outer circuit is from the more reactive metal to the less reactive metal which causes a current to flow.

The difference between sacrificial protection and cathodic protection is that in sacrificial protection, bars of a more reactive metal are attached to the metal to be protected and this more reactive metal corrodes, protecting the less reactive metal. But in cathodic protection, the metal to be protected is made the cathode and a more reactive metal is made the anode. Oxidation happens at the anode and the cathode stays protected.

I hope you got it :)
 
ZaqZainab

ZaqZainab

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Maro ashroof said:
assalamu alaykom...
chemistry question:
can someone please explain for me how does a voltaic cell work and what are the differences between sacrificial protection and cathodic protection?
Thank you in advance:)
Click to expand...
Sacrificial protection consists of placing a piece of easily corroded material upstream of the metal you are trying to save. These pieces of metal are called coupons. Place the coupon in a process upstream of the pipes requiring the protection and the theory is that the positively charged particles in the process stream will aggressively attack the coupon and be expended before they reach the protected metal.
Both systems of protection work. Cathodic protection requires electrical power and sacrificial protection requires regular changing of the coupons.
Cathodic protection is typical for tanks while the coupons are normally used in flow situation like water pipes.
 
M

Maro ashroof

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Iridescent said:
Voltaic cell: It changes chemical energy into electrical energy. It works by the difference between the reactivity of two metals. The more reactive metal is made the anode which is connected to the negative terminal of the volt meter. The flow of electrons in the outer circuit is from the more reactive metal to the less reactive metal which causes a current to flow.

The difference between sacrificial protection and cathodic protection is that in sacrificial protection, bars of a more reactive metal are attached to the metal to be protected and this more reactive metal corrodes, protecting the less reactive metal. But in cathodic protection, the metal to be protected is made the cathode and a more reactive metal is made the anode. Oxidation happens at the anode and the cathode stays protected.

I hope you got it :)
Click to expand...
thank you so much :)
 
M

Maro ashroof

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ZaqZainab said:
Sacrificial protection consists of placing a piece of easily corroded material upstream of the metal you are trying to save. These pieces of metal are called coupons. Place the coupon in a process upstream of the pipes requiring the protection and the theory is that the positively charged particles in the process stream will aggressively attack the coupon and be expended before they reach the protected metal.
Both systems of protection work. Cathodic protection requires electrical power and sacrificial protection requires regular changing of the coupons.
Cathodic protection is typical for tanks while the coupons are normally used in flow situation like water pipes.
Click to expand...
thank you so much :)
 
Princess Raven

Princess Raven

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hey guys for electrolysis
when they say the solution is aques....is it conctrated or dilute? like how do we know?
 
Nita Mahajan

Nita Mahajan

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cookies&cream said:
Q.1. Ans. is C, because when two gases have the same mole ratio, they have the same volume. Further explanation?
no. of moles of NO= vol./24 = 20/24 = 0.8333...
According to equation, ratio NO:NO2 equals 2:2, so both have same no. of moles. Therefore,
no. of moles of NO2= 0.8333... so, vol. of NO2= 20

Q.2. Not really sure, but I'm guessing it's A.. Because for 2 moles of Cu ions, 2 thiosulfate ions were needed for the I2 formed, so 1 mole of Cu needs 1 mole of thiosulfate. Correct me if I'm wrong, please.

Q.7. a) no. of moles of potassium permanganate = vol. x con. = (16.7/1000) x 0.03 = 5.01 x 10^-4
b) mole ratio manganate : iron = 1:5 , so, no. of moles of Fe ions = (5.01 x 10^-4) x 5 = 2.505 x 10^-3
c) no. of moles of anhydrous compound = 2.505 x 10^-3 (Equation above is ionic, so parts of the compound were crossed out, but mole no. is still the same)
So mass of compound = mol. x RMM = (2.505 x 10^-3) x 284 = 0.71142
d) mass of water = hydrated mass - anhydrous mass = 0.98 - 0.71142 = 0.26858 g ----> 0.269 g
no. of moles = mass/RMM = 0.269/18 = 0.0149 <--- divide by no. of moles of anhydrous compound
so, X= 0.0149/(2.505 x 10^-3) = 5.96 = 6 (This is how my teacher taught it)
Q.9 & 10. Never studied concentration of ions in a solution before o.o (teacher wasn't the best)

Hope I helped though :)
Again, please correct me if I'm wrong. Good luck.
Click to expand...


but for question 1, d answer is A... even 1 thought the answer was C
The answer for question 2 is also A...so u r correct there!
All the answers for question 7 r correct.. but i wanted to ask for part 7(c), that why r the no. of moles same for Fe ions and the hydrated salt? Is it always same? How do v know when it is same?
anyways thnks for ur help!!
 
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