User23
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Ok so basically, I'm getting a bit confused over exothermic and endothermic reactions. I don't get how in exothermic reactions, there is more energy in the reactants than in the products and yet the products release more energy? (BOND FORMATION)
PLEase help me
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Kamil3
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bonds brokEN = ENdothermic
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z33
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basicallllyyyyy

bond breaking is ENDOthermic - think of it like breaking a snickers bar in half. You're gonna need to use energy to do it. Bond formation is the opposite - exothermic - exo = exit, energy exits- energy released

EDIT:

energy is needed to break bonds
and energy is released when bonds are formed

to see whether a reaction is endothermic or exothermic overall

we see how much energy is needed to break the bonds

then we see how much energy is released when new bonds are formed

and if more energy is needed to break them than make new ones (more to break reactants than make products) - the reaction is endothermic

if more energy is released when new bonds are made than energy needed to break the bonds (more energy released when products are made than when reactants are broken) the reaction is exothermic
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username1567177
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the only way to conker this is loads and loads of past papers trust me i was like you if not worse and i get it now thx to my awesome science teacher and the aqa website
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z33
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(Original post by xGCSE_Studentx)
the only way to conker this is loads and loads of past papers trust me i was like you if not worse and i get it now thx to my awesome science teacher and the aqa website
don't forget chemguide! that **** gives me life. it's the Google of chemistry A - levels
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username1567177
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(Original post by z33)
don't forget chemguide! that **** gives me life. it's the Google of chemistry A - levels
can't say i've heard of it
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toonervoustotalk
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Bendo mexo
Bond breaking- endothermic
Bond making-exothermic
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z33
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(Original post by xGCSE_Studentx)
can't say i've heard of it
legit... get on it now

it's chemistry heaven :drool:

dunno if there's gcse stuff on there though so

but its still BEAUTIFUL
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username1567177
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(Original post by z33)
legit... get on it now

it's chemistry heaven :drool:

dunno if there's gcse stuff on there though so

but its still BEAUTIFUL
no i've checked it out it doesn't do gcse stuff but ive got enough resources for that

Im planning on picking chemistry for a level so it'll come in handy - thanks for recommending it tho x
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User23
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(Original post by z33)
basicallllyyyyy

bond breaking is ENDOthermic - think of it like breaking a snickers bar in half. You're gonna need to use energy to do it. Bond formation is the opposite - exothermic - exo = exit, energy exits- energy released

EDIT:

energy is needed to break bonds
and energy is released when bonds are formed

to see whether a reaction is endothermic or exothermic overall

we see how much energy is needed to break the bonds

then we see how much energy is released when new bonds are formed

and if more energy is needed to break them than make new ones (more to break reactants than make products) - the reaction is endothermic

if more energy is released when new bonds are made than energy needed to break the bonds (more energy released when products are made than when reactants are broken) the reaction is exothermic
Yeah, I understand this. However, for example, say you've got Mg+ 2HCl -> MgCl2 + H2. I'm aware that this is an exothermic reaction but the thing is that in the energy level diagram it shows that the reactants have more energy than the products but I thought it would be the other way round because when the bonds are made (MgCl2 + H2) this would release a whole lot more heat energy than the energy needed to break the bonds (Mg+ 2HCl).
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z33
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(Original post by User23)
Yeah, I understand this. However, for example, say you've got Mg+ 2HCl -> MgCl2 + H2. I'm aware that this is an exothermic reaction but the thing is that in the energy level diagram it shows that the reactants have more energy than the products but I thought it would be the other way round because when the bonds are made (MgCl2 + H2) this would release a whole lot more heat energy than the energy needed to break the bonds (Mg+ 2HCl).
yeah because in an exothermic reaction energy is released, which is what that arrow represents. How are you gonna release more energy than you started off with? that's impossible

if it's going up from reactants to products, it means energy going in not that its increasing
going down from reactants to products means energy going out not that it's decreasing
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User23
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(Original post by z33)
yeah because in an exothermic reaction energy is released, which is what that arrow represents. How are you gonna release more energy than you started off with? That's impossible

if it's going up from reactants to products, it means energy going in
going down from reactants to products means energy going out
ohhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh hhhhhhhhhhhhhhh ok thank you xxxxxxxxxxxxxx
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z33
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(Original post by User23)
ohhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh hhhhhhhhhhhhhhh ok thank you xxxxxxxxxxxxxx
haha no problem
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