It's been a long while since chem, but perhaps this will put you on the path. When they're talking about "half reaction" I believe they're referring to one side or the other, of the balanced equation -- what forms from what. In the case of solid copper and silver nitrate, the copper "takes" the NO3 and leaves the silver, previously in solution, to remain as a solid.
Cu + 2AgNO3 ---> Cu(NO3)2 + 2Ag
Methanal (formaldehyde) reacts with Tollens' reagent, which contains silver ions in an alkaline solution, to produce silver metal. During this reaction, methanal is oxidized to formic acid, while the silver ions are reduced to metallic silver, resulting in a characteristic silver mirror on the inner surface of the reaction vessel. This reaction is a classic test for aldehydes, as they can reduce Tollens' reagent, unlike most ketones.
When silver is mixed with water, a reaction may occur where silver oxidizes and releases silver ions into the water. This can result in a color change in the water as the silver ions may form a complex with water molecules. However, this reaction is generally slow and not as dramatic as with more reactive metals.
Yes, nickel can act as a reducing agent in a reaction with silver ions. In this case, nickel atoms would be oxidized (lose electrons) to form nickel ions, while the silver ions would be reduced (gain electrons) to form silver atoms. The nickel atoms are undergoing oxidation themselves, thus acting as the reducing agent in the reaction.
The spectator ions are Ag+ and (NO3)-.
A white solid called silver chloride is formed when silver nitrate is added to a solution of cobalt chloride. This reaction is a double displacement reaction where the silver ions from silver nitrate replace the chloride ions from cobalt chloride to form the insoluble silver chloride precipitate.
In this reaction, the zinc metal will displace silver ions in the solution because zinc is more reactive than silver. As a result, zinc will oxidize to form zinc ions while silver ions from the silver nitrate will be reduced to form silver metal. This reaction is an example of a single displacement reaction.
Ag+ (apex)
One example of an oxidation-reduction reaction is the reaction between copper metal and silver nitrate solution. In this reaction, copper metal is oxidized (loses electrons) to form copper ions, while silver ions from the silver nitrate solution are reduced (gain electrons) to form solid silver metal. This results in a redox reaction where electrons are transferred from copper to silver ions.
In the reaction between chlorine and iodine ions, a redox reaction occurs where chlorine ions oxidize iodine ions to form diatomic iodine molecules. The chlorine ions are reduced to form chloride ions. This reaction can be represented as Cl2 + 2I- -> 2Cl- + I2.
With what? Not enough detail, but silver is not very electropositive. Pretty much any compound or chemical entity can be involved in a redox reaction of some kind. The obvious redox reaction involving silver nitrate would involve silver ions being reduced to silver metal, plus some corresponding oxidation reaction.
The most likely redox reaction that would occur is the reduction of silver ions to silver metal by copper atoms, with copper atoms oxidizing to copper ions in the process. This reaction would lead to the displacement of silver ions by copper atoms in the solution.
The reaction between silver nitrate and potassium iodide forms silver iodide precipitate and potassium nitrate. This reaction is a double displacement reaction where the silver ions from silver nitrate switch places with the potassium ions in potassium iodide.
The silver ions are being reduced to silver atoms during electroplating. In this process, electrons are gained by the silver ions, causing them to be reduced to elemental silver atoms, which get deposited onto the flatware.
In this reaction, copper is acting as a reducing agent, because it is undergoing oxidation itself as it loses electrons to form copper(II) ions. Silver ions from the silver nitrate are gaining electrons and being reduced to form solid silver metal.
The spectator ions in the reaction between silver sulfate and barium nitrate are nitrate (NO3-) ions and sulfate (SO4^2-) ions. These ions do not participate in the formation of the precipitate (barium sulfate) and remain unchanged throughout the reaction.
Silver nitrate can react with tetrachlorocobaltate to form silver tetrachlorocobaltate, Ag2CoCl4. This reaction involves the replacement of the nitrate ions with tetrachlorocobaltate ions.
A double displacement reaction has occurred. The potassium and silver ions have swapped partners to form silver chloride and potassium acetate, respectively. This reaction is driven by the exchange of ions between the compounds.