Question

of the following conditions, which will cause the reaction rate to be the slowest?
40 °c, small particles, stirring
20 °c, large particles, stirring
20 °c, large particles, no stirring

Explanation:

Reaction rate is affected by temperature, particle size, and stirring. Lower temperature (slower particle motion), larger particles (smaller surface area for reaction), and no stirring (less collision between reactants) all decrease reaction rate. Comparing the options: 40°C (higher temp) + small particles + stirring (fastest); 20°C + large particles + stirring (faster than no stirring); 20°C + large particles + no stirring has the lowest temp, largest particles, and no stirring, so the slowest rate.

Answer:

C. 20 °C, large particles, no stirring (assuming the third option is labeled C; if original labels differ, adjust to match, e.g., if third option is the last one, state its text with identifier as per original, but here with the given options, the third option "20 °C, large particles, no stirring" is the correct one for slowest reaction rate)