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Answer: (3) ppm
Explanation: Concentration is defined as the amount of solute dissolved in a known amount of the solvent or a solution.
Parts per million (ppm) is used to express the concentration when a very small quantity of solute is present in a large quantity of the solution. It is defined as the mass of solute present in one milion
parts by mass of the solution.
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L/s is used to express flow rate.
J/g is used to express energy per unit mass.
kPa is used to express pressure.
The reaction is a displacement reaction. Iron is more reactive than copper. Hence, it displaces copper,forming iron II sulfate and copper metal.
This reaction is an exothermic reaction, hence it releases energy. The colour change indicates that iron has displaced copper.