Everything Science Grade 12

CHAPTER 4. ELECTROCHEMICAL REACTIONS 4.2

A

+

salt -

bridge

CuSO 4 (aq) ZnSO 4 (aq)

electronflow

Cu Zn

+

Results:

During the experiment,you should have noticedthe following:

• When the U-tube containing the Na 2 SO 4 solution was absent, there was
  no reading on the ammeter.


• When the U-tube containing the Na 2 SO 4 solution was connected,a read-
  ing was recorded on theammeter.


• After the plates had been connected directly toeach other and left for a
  day, there was a change in their mass. The mass of the zinc plate de-
  creased, while the massof the copper plate increased.


• The direction of electron flow is from the zincplate towards the copper
  plate.

Conclusions:

When a zinc sulphate solution containing a zincplate is connected by a U-

tube to a copper sulphate solution containing acopper plate, reactionsoccur

in both solutions. The decrease in mass of the zinc plate suggests that the zinc

metal has been oxidised. The increase in mass of the copper plate suggests

that reduction has occurred here to produce more copper metal. Thiswill be

explained in detail below.