a change in which factor will affect the rate of reaction only when gases are involved?\no temperature\no…

Answer:

B. pressure

Explanation:

Step1: Analyze temperature

Temperature affects reaction - rate for all states (solid, liquid, gas). It increases the kinetic energy of reactant particles in general.

Step2: Analyze pressure

Pressure mainly affects the rate of reaction for gases. According to the ideal - gas law ($PV = nRT$), increasing pressure on a gas is equivalent to increasing its concentration (when temperature and volume are constant), which can increase the frequency of collisions between gas particles and thus the reaction rate. Liquids and solids are incompressible, so pressure has little to no effect on their reaction rates.

Step3: Analyze surface area

Surface area affects the rate of reaction for solids (in heterogeneous reactions). A larger surface area provides more sites for reactant - particle collisions, but it is not specific to gases.

Step4: Analyze concentration

Concentration affects the rate of reaction for all states. Higher concentration means more reactant particles available for collisions, regardless of whether they are in the gas, liquid, or solid state.