If 5.0 g of marble reacts with 25.0 cm3 hydrochloric acid, which of the following combinations has the fastest reaction rate?

The reaction rate is determined by the collision frequency and effectiveness of collisions between reactant particles. A higher concentration of reactants generally leads to a faster reaction rate because it increases the likelihood of successful collisions. In this case, the concentration of hydrochloric acid is given in terms of mol dm^-3. The higher the molarity (mol dm^-3) of the hydrochloric acid, the greater the concentration of HCl particles in the solution. Comparing the options, we can see that the combinations with higher molarities of hydrochloric acid (2.5 mol dm^-3) are likely to have a faster reaction rate than the combinations with lower molarities (2.0 mol dm^-3). Furthermore, the option involving powdered marble instead of marble chips can also contribute to a faster reaction rate. Powdered marble provides a larger surface area for the reaction to occur, allowing for more collisions between the marble particles and the hydrochloric acid. Therefore, the combination of powdered marble and 2.5 mol dm^-3 HCl(aq) is most likely to have the fastest reaction rate among the given options.