chem help!

[hanna67]

can sm1 plz explain for me how d cell works...n do we place Zn at the negative or positive terminal? n y?
thnx in advance

 

[XPFMember]

do we place Zn at the negative or positive terminal?

see it depends ,i guess u a=r talking abt simple cell,so we do not keep it ourselves cuz we do not connect a battery in a simple cell of course.as we know that electron flow is from anode to cathode so the more reactive metal becomes the anode!!

 

[Tk :)]

hey
ill just post my teacher's notes!!
so,
the cell is made of
two different metal rods that differ in their reactivity
the more reactive metal acts as the negative electrode
the less reactive metal acts as the posotive electrode
the metal rods are dipped in the electrolyte
the electrolyte is mostly dilute acid or any aqueous solution containing free ions
the more reactive metal will always lose electrons and move into the electrolyte as +ve ions
the electrons from the -ve rod always move to the +ve rod
the +ve rod doesnt take part in any reaction.it only acts as a passagefor the electrons coming from the -ve rod
the electrons from the +ve rod are picked up by the +ve from the electrolyte
the -ve(more reactive) rod slowly dissolves
gas bubbles appear near the +ve rod
the movement of electrons from the -ve to the +verod produces current
the greater difference in the reactivity of metals, the greater the current produced.
hope this helps

 

[LoayTYS]

do we place Zn at the negative or positive terminal?

see it depends ,i guess u a=r talking abt simple cell,so we do not keep it ourselves cuz we do not connect a battery in a simple cell of course.as we know that electron flow is from anode to cathode so the more reactive metal becomes the anode!!

I am sorry but electrons move from cathode to anode (negative to positive in cell) and the more reactive metal is the cathode and the less reactive is the anode

 

[XPFMember]

I am sorry but electrons move from cathode to anode (negative to positive in cell) and the more reactive metal is the cathode and the less reactive is the anode

Actually electrons do flow from negative to positive however in a simple cell anode is negative not positive(as in the electrolytic cell )and this is one of the differences between the two.
Remember that electron flow is ALWAYS from anode to cathode whether it is an electrolytic cell or a simple cell!
I am sure abt. this cuz i wrote what i knew in the post before but when u said that there's a mistake i searched on the net and came to a conclusion it is as i said!!any way if u still doubt that , check this link
I know it is galvanic cell which is little bit different from simple cell but the concept is almost same!!

 

[niassu]

but do u meanthat in an electrolytic cell also eletrons flow from anode?? :|
well, i think its true as if the anode in electrolytic cell is +ve and -ve ions are attracted to it where they lose electrons then electrons will move from anode right??
while in galvanic cell it moves from cathode i mean more reactive metal to low reactive one

 

[XPFMember]

for both cells electrons flow from anode to cathode!!
but in electrolyte cell anode is positive(thus attracts anions)
and in simple cell anode is negative!!

 

[hanna67]

thank u everyone i think i understood....so as a conclusion...in tht case we put zinc at the cathode..cz its more reactive?
thnx again

 

[XPFMember]

no we put the more reactive metal at the anode(simple cell)!!!!!!!!
see electron flow is from:
---anode to cathode
---negative to positive
---more reactive to less reactive
so we can say that more reactive metal is the anode which is negative!!

 

[hanna67]

yea i agree n thnx....bt wait isnt the anode positive and cathode negative????

 

[XPFMember]

it is but in the electrolytic cell,in simple cell it is the opposite,remember in both cells electron flow will be from anode to cathode,and as i told u in my earlier post that electron flow in simple cell is from:
---anode to cathode
---negative to positive
then the anode shud be negative right.

 

[hanna67]

yeaaa ok now i got it...thts only in the cell ryt?....ok thnx alooot!!!

 

[XPFMember]

anode to cathode rule applies to both electrolytic as well as simple cell!!
also remember that oxidation always takes place at anode,
In electrolytic cell,anions lose electrons and in simple cell,the more reactive -having greater tendency to become ions--lose electrons!!

 

[hanna67]

yup tht really helped thank u