Answer: (B.) The reaction rate is highest when sodium powder is used.
Explanation:
Five factors that affect the rate of reactions are : Temperature, concentration, nature of catalyst, chemical nature of reactants and nature of subdivision of particles (heavier size versus smaller or powdered particles).
Nature of subdivision of particles :
Since reactions occur at the boundary between two phases therefore tyhe rate of reaction depends on surface contact available between them. A powdered particle has generally more surface area than the particle in solid form.
