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Biology; Chemistry; Physics: Post your doubts here!

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(i) Electrical Energy from the main supply converts into chemical energy which eventually gets stored in the battery.
(ii) Electrical energy is converted to kinetic energy so sound energy is produced.
Your first part is correct and it is the ANSWER but the second part is incorrect and is not even required, Electrical energy actually changes to chemical energy and thermal (heat) energy not sound energy; besides, the question asks for USEFUL energy outputs.
 
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Your first part is correct and it is the ANSWER but the second part is incorrect and is not even required, Electrical energy actually changes to chemical energy and thermal (heat) energy not sound energy; besides, the question asks for USEFUL energy outputs.
(ii) is just to add an extra bit of knowledge.
 
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thanks to both of you :) by the way Saad, what if it had not included the word useful? And what does it really means by useful?
 
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If it hadn't included the word useful then we would have added Heat Energy (Thermal Energy) since this is a common day example that our cellphones heat up when they are being charged this shows that energy is being WASTED in form of heat. By useful they mean that the energy conversions that are actually performing the task required, here the heat energy is wasted whereas only the chemical energy is used to charge the battery hence only CHEMICAL energy is useful. Hope you get it. :)
 
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If it hadn't included the word useful then we would have added Heat Energy (Thermal Energy) since this is a common day example that our cellphones heat up when they are being charged this shows that energy is being WASTED in form of heat. By useful they mean that the energy conversions that are actually performing the task required, here the heat energy is wasted whereas only the chemical energy is used to charge the battery hence only CHEMICAL energy is useful. Hope you get it. :)

yup got it. Thanks very much. I've actually never noticed this keyword before
 
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i thought iv already done my chemistry preparation and when I started an atp paper and checkd...i was shocked! please help me with question 2 of this paper. PLEASE! its very urgent! http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_s06_qp_4.pdf the mark scheme says tht the gas in tube y will be twice as much as the gas in tube x. why is it? can sum1 please explain :-/
It's kinda easy :p
We know that the sulphate ion is not given preference of discharge over hydroxide (in other words, sulphate ions are never discharged) therefore hydroxide ions, i.e. oxygen gas (negative ion) will give off at the anode (tube X) and the other Hydrogen ions (H+) will form and hence hydrogen will be formed in tube Y. Now from waters composition we can simply see that twice the amount of HYDROGEN ions will be present when compared to the HYDROXIDE ions (H2O) hence tube Y has double the volume of gas. Hope that helps. :)
 
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It's kinda easy :p
We know that the sulphate ion is not given preference of discharge over hydroxide (in other words, sulphate ions are never discharged) therefore hydroxide ions, i.e. oxygen gas (negative charge) will give off at the anode (tube X) and the other Hydrogen ions (H+) will form and hence hydrogen will be formed in tube Y. Now from waters composition we can simply see that twice the amount of HYDROGEN ions will be present when compared to the HYDROXIDE ions (H2O) hence tube Y has double the volume of gas. Hope that helps. :)
i get the point that hydrogen will be produced more in quantity than oxygen. BUT; that doesnt ake it twice as much. twice as much will be there only when there is water. but we have sulphuric acid too and it produces equal amounts of h+ ions and OH- ions. lets say 1 unit each. and then v have 2 units of hydrogen and 1 unit of oxygen. that makes 3 units of hydrigen and 2 units of oxygen. which isn't the double :-/
 
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i get the point that hydrogen will be produced more in quantity than oxygen. BUT; that doesnt ake it twice as much. twice as much will be there only when there is water. but we have sulphuric acid too and it produces equal amounts of h+ ions and OH- ions. lets say 1 unit each. and then v have 2 units of hydrogen and 1 unit of oxygen. that makes 3 units of hydrigen and 2 units of oxygen. which isn't the double :-/
Do you know why sulphuric ion does not discharge? This is because it is very reactive and forms sulphuric acid again after ionising.
Hence, the quantity of hydrogen is in terms only double that of hydroxide (from H2O) but in actual experiments it would be slightly more than double because of the extra hydrogen ions.
 
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They are next to sulphuric acid in discharge series. They discharge in preference to sulphate ions but don't discharge in aqueous solutions since hydroxide more easily discharges. Hope that helps :)
hmm yup thnx :)
btw do carbonates discharge???
 
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