How many grams of nickel (+2) are required to replace all of the silver when 15.55 grams of agno3 are present?

2AgNO3 + Ni2+  = Ni(NO3)2 + 2Ag+

From the reaction, it can be seen that AgNO3 and Ni2+ has following amount of substance relationshep:

n(AgNO3):n(Ni)=2:1

From the relationshep we can determinate requred moles of Ni2+:

n(AgNO3)=m/M= 15.5/169.87=0.09 moles

So, n (Ni)=n(AgNO3)/2=0.045 moles

Finaly needed mass of Ni2+ is:

m(Ni2+)=nxM=0,045x58.7=2.64g

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.