Agalvanic cell has the overall reaction: zn(s) 2eu(no3)3(aq)  zn(no3)2(aq) 2eu(no3)2(aq) which is the half reaction occurring at the anode

The half reaction occurring at anode is

Explanation:

In a chemical cell, substance getting oxidized always act as anode and the one getting reduced always act as cathode.

Oxidation reaction is defined as the reaction in which an atom looses its electrons. Here, oxidation state of the atom increases.

Reduction reaction is defined as the reaction in which an atom gains electrons. Here, the oxidation state of the atom decreases.

For the given chemical cell reaction:

Oxidation half reaction (anode):  

Reduction half reaction (cathode):      ( × 2 )

Here, zinc is loosing electrons and is getting oxidized and europium is gaining electrons and loosing electrons.

Hence, the half reaction occurring at anode is

it can be observed without changing the identity of the object.

it depends on what substance you're talking about as well as many other factors. in quantum mechanics, the observation of particles affects the observers ability to measure certain properties. for example: you can know the velocity of a particle, but you can't know it's position; or you can know it's position, but not it's velocity. it's like trying to find out where a grain of sand is by throwing other grains of sand at it. once you find out where it is, it's been moved. it's also like trying to find an answer to the question of whether or not a tree falling in a forest makes a sound if nobody is there to hear it. paradoxically, the only way to find out is to be there and hear it.