Dashmesh public school Chemistry -project
Session :- 2015-16 Topic:-
“ Study o presence o o!alate ion content in "ua#a ruit at di$erent sta%es o ripenin%&'
(ame
:- )ahul*harti
Class
:- !ii + *
)oll no
:- 1
Certifcate
This is to certiy certiy that )ahul*harti, a student o class XII-B XII-B has successully completed the research on the below mentioned mentioned CHEMIT! CHEMIT!" I#$ETI%& I#$ETI%&T'! T'!" " (!')ECT durin* the year +.-+/ in partial ulfllment o chemistry practical e0amination e0amination conducted by CBE ,#ew1elhi2
2222222222222222222222222222 22222222222 3 E0aminer 4 Inchar*e4
2222222222222222222 3Teacher
&c5nowled*e-ment I , !ahulBharti !ahulBharti o class XII B e0press my *ratitude to my school authorities or allowin* me to underta5e the pro6ect entitled “ Study o presence o o!alate
ion content in "ua#a ruit at di$erent sta%es o ripe ri peni nin% n%&' &' , naturally could not ha7e
done 6ustice to my delicate assi*nment , had i not been pri7ile*ed to *et the animate *uidance rom Mrs2 &n6u %upta , Chemistry teacher or hi*her econdary Classes o 1ashmesh (ublic chool2 I also e0press sincere than5s to my amily who e0tended helpin* hand in completin* this pro6ect2 pro6ect2 - !ahul Bharti
Introduction EMF , Terminal Voltage & Internal Resistance of a Cell/Battery &n Electric Cell or Battery is Battery is a power *eneratin* de7ice which *enerates an Electromoti7e 8orce in between it9s two terminals2 terminals2 &lon* with the the de7eloped EM8 , an electric cell and battery also ha7e some internal resistance , which in-tern e:ect9s it9s terminal 7olta*e2 & detailed descriptions o these parameters o a battery and cell are *i7en below;
lectromoti#e .orce: EM8 o a cell or battery is the total 7olta*e or potential di:erence de7eloped between the two terminals o the cell
battery2 1ue to the internal resistance o a cell
=here, I is the total current bein* drawn rom the cell
,nternal resistance resistance:: 1ue to 7arious physical and chemical constraints the electron when tra7ellin* rom the ne*ati7e terminal o a cell or battery to the positi7e terminal , e0periences some resistance2 This resistance e0perienced by an electron or current inside the cell or battery is called the internal resistance o the cell or battery2 uch resistance is caused due to resistance o electrodes , deposition or e0tra materials in electrolytes and electrodes o a cell2 Is the Internal resistance resistance o a cell or battery which resists the >ow o electron throu*h the cell
&nd the (otential di:erence across the load or the Terminal $olta*e can be calculated as;
'B)ECTI$E ; To To study the 7arious 7arious actors on on which the internal internal resistance resistance o a cell depends2
&pparatus ;& (otentiometer , a battery 3battery eliminator4 , two way 5eys , a rheostat o low resistance , a *al7anometer , a hi*h resistance , an ammeter , a cell , a )oc5ey )oc5ey , a set s?uare , connectin* wires , water bath , thermometer3-@C4 , burner , tripod stand , wire *au*e 2
theory ; The internal internal resistance resistance o a cell cell is the resistance resistance o:ered o:ered by its electrolyte to the >ow o ions 2 The internal resistance o a cell •
is directly proportional proportional to the distance between the electrodes2
•
• •
is in7ersely proportional to acin* surace area o the electrodes in electrolyte2 decreases with increase in temperature o electrolyte2 is in7ersely proportional to concentration o electrolyte2
The internal internal resistance resistance o a cell cell is *i7en by
rA3 where
l1
,
l2
l 1− l 2 l1
4!
are the balancin* len*ths without resistance resistance
and with resistance 3shunt4 , respecti7ely and ! is the shunt resistance resistance in parallel with the *i7en cell2
procedure procedure ;tep 2 1raw the circuit dia*ram showin* the scheme o connections2 +2 Clean the ends o the connectin* wires wires with sand paper and ma5e ti*ht connections accordin* to the circuit dia*rams2 2 Ti*ht the the plu*s o the resistanc resistance e bo02 2 Chec5 Chec5 the the e2m2 e2m222 o the the batte battery ry and and cell cell and and see that that e2m22 and see that e2m22 o the battery is more than that o *i7en cell ,otherwise null or balance point will not be obtained 3ED E42 .2 Ta5 a5e e ma0imu ma0imum m curren currentt rom rom the the battery battery , ma5in* ma5in* rheostat resistance small2
/2 To test the corrections o the connections ' 3insert the plu* in the 5ey K and note the ammeter readin* 2Ta5e out + ohm resistance plu* rom resistance bo02 (lace the 6o5ey frst at the end ( o the wire and then at the end F2 I the *al7anometer shows de>ection in opposite direction direction in the two cases the connections are correct42 1
G2 =ith ithout out ins insert ertin* in* the plu plu* * in in the the 5ey K ad6ust the rheostat so that a null point is obtained on the th wire o potentiometer p otentiometer22 2
2 Insert Insert the + + ohm ohm plu plu* * bac5 bac5 in the pos positi ition on in in resistance bo0 and by sli*htly ad6ustin* the 6oc5ey near the pre7ious obtained position o null point, obtain null point position accurately, usin* a set s et s?uare2 2 Meas Measur ure e th the e ba bala lanc ncin in* * len len*t *th h and the end ( o the wire2
l1
between the point
2 Ta5e out the + ohm plu* a*ain rom the resistance bo0 !2B2 introduce plu*s in the 5ey K ,as well as in 1
5ey K 2 Ta5e out small resistance 3-. J4 rom the resistance bo0 ! connected in parallel with the cell2 2
2 lide the 6oc5ey 6oc5ey alon* the potentiometer potentiometer wire wire and obtain null point2 +2 Insert + ohms plu* bac5 in its position in in R.B. and i necessary ma5e ma5e urther ad6ustment or sharp null point2 2 Measure the balancin* balancin* len*th len*th
l2
rom end (2
2 !emo7e the plu* plu* 5eys 5eys at K and K 2=ait or some time and or the same 7alue o current 3as shown by ammeter4 repeat the steps G to 2 .2 !epeat the obser7ations obser7ations or di:rent di:rent 7alues o ! repeatin* repeat in* each obser7ation twice2 1
2
/2 Calculate the internal internal resistance resistance o cell by usin* the the abo7e relation or r2 r2 tep + To T o see the e:ect e:ect o distance between the electrodes on internal resistances 5eepin* the other actors constant ,7ary separation between electrodes electrodes and measure internal resistance resistance in each case2 tep To T o see the e:ect e:ect o the temperatur temperature e o electrolyte electrolyte on internal resistance by 5eepin* other actors constant2 Keep primary cells in water bath to heat the electrolyte2 1etermine the internal resistance at 7arious temperatures2 tep To T o see the e:ect e:ect o concentration concentration 3nature4 3nature4 o electrolyte on internal resistance by ;Keepin* the other actors constant , decrease concentration o electrol electrolyte yte by addin* addin* the distilled water and determine internal resistance o cell in each case 2
obser7ations ;-
2#o2
&mmeter !eadin*
(os2 o null point 3 cm 4
3&4
=ith ! 3l 4
rA3 ( l −l )/ l
hunt !esistance
=ithout ! 3 l+ 4
1
2
1
4! J
!3J4
2 +2 2
Table Table or e:ect e:ect o separation separation between electrode electrodes s ;2#o2
eparation between Electrodes-d 3cm4
Balanci n* len*th 3cm4 3 l 4
Balancin * len*th
rA3 ( l −l )/ l 1
2
1
r
4!
3cm4 3l+4
3J4
2 +2 2
table or e:ect o temperature ;2#o2
2 +2 2
Temperature
l
3T4 @C
3cm4
l+ 3cm4
!esista nce ! 3J4
rA3
l 1− l 2 l1
3J4
4!
Tr Tr 3JK4
Conclusions ;2 The Electromoti7e Electromoti7e 8orce 8orce o the cell is constant and is e?ual to E A 2 $olt +2 The internal resistance resistance o a cell is directly proportional proportional to the separation between the electrodes2 electrodes2 2 The internal resistance resistance o a cell is in7ersely proportional proportional to the area o the electrodes dipped in electrolyte2 2 The internal resistance resistance o a cell is in7ersely proportional proportional to the temperature o electrolytes2 .2 The internal resistance resistance o a cell is in7ersely proportional proportional to the concentration o the electrolyte2 electrolyte2
(recautions (recautions ;2 The connections connections should be neat , clean and ti*ht2 ti*ht2 +2 The plu*s should be introduced introduced in the 5eys 5eys only when the obser7ations are to be ta5en2 2 The positi7e polls o the battery battery E and cells E and and E+ should , all be connected to the terminal at the Lero o the wires2 2 The 6oc5ey 6oc5ey 5ey 5ey should not be rubbed alon* the wire2 It should touch the wire *ently2 .2 The ammeter readin* readin* should remain remain constant or a particular set o obser7ation2 I necessary , ad6ust the rheostat or this purpose2 /2 The e2m22 e2m22 o the battery should be *reater than the e2m22Ds o the either o the two cells2
G2 ome hi*h resistance resistance plu* should always always be ta5en ta5en out rom resistance bo0 beore the 6oc5ey is mo7ed alon* the wire2 2 The e2m22 e2m22 o the battery should be *reater than that o the cell2 2 8or 8or one set o obser7ation the ammeter readin* readin* should remain constant2 2 Current Current should be passed or short time time only , while fndin* the null point2 2 !heostat should should be ad6usted so that that initial null point lies on last wire o the potentiometer2 +2 Cell should not be disturbed durin* e0periment2 e0periment2 2 )oc5ey )oc5ey should not be rubbed a*ainst the the potentiometer potentiometer wire2
sources o error ;2 The au0iliary battery battery may not be ully char*ed2 char*ed2 +2 The potentiometer potentiometer wire may not be o uniorm crosscrosssection and material density throu*hout its len*th2 2 End resistances resistances may not be Lero2 Lero2
BIBBI'%!&(H" https;<
