Which of the following best represents the rate law for the reaction A(solid) + 2B(aq) -> D(solid) given that A is a solid and D is a solid and B is in solution?

Prepare for the Plovdiv Entrance Exam. Equip yourself with comprehensive study materials, including multiple choice questions and flashcards. Ensure success in your examination!

When a solid reactant is involved with a species in solution, the solid’s amount isn’t treated as a variable in the rate law. The rate depends on how many reactant molecules in solution collide with the solid surface, and the solid’s surface area (in practice) is considered effectively constant during the reaction. So the rate law focuses on the solution-phase reactant, B, and its power reflects how many B molecules participate in the rate-determining step.

If two B molecules are involved in the slow step, the rate is proportional to [B] squared. The solid A simply provides the surface; it does not appear in the rate law. Therefore the rate expression is V = k [B]^2.

Including [A] would imply the solid’s concentration changes the rate, which isn’t how rate laws for solids are treated, and adding terms like k + [A] + [B]^2 or multiplying by [A] would misrepresent the role of the solid.