Answer:
            The number of representative particles in 11.5 moles of potassium bromide are 6.92 × 10²⁴ formula units of KBr.
Solution:
             As we know that 1 mole of any substance exacly contains 6.022 × 10²³ particles. Mathematically;
             Moles  =  Number of Particles ÷ 6.022 × 10²³
Solving for Number of Particles,
             Number of Particles  =  Moles × 6.022 × 10²³
Putting values,
             Number of particles  =  11.5 mol × 6.022 × 10²³ particles.mol⁻¹
             Number of Particles  =  6.92 × 10²⁴ formula units of KBr