Round 8: Tossup 4

This quantity is converted to a related “tracer” by an expression containing the derivatives of the natural logs of activity coefficient and mole fraction. The decay constant used to calculate particle size in dynamic light scattering is proportional to this quantity times the Bragg wave vector squared. Negative values of this quantity (15[1])may arise in multicomponent systems when using the Maxwell-Stefan equation. This quantity is negative during (*) spinodal decomposition since one process occurs “uphill.” For an ideal gas, this quantity equals a constant times the product of mean velocity and mean free path. This quantity equals mobility times Boltzmann’s constant times temperature according to the Einstein relation. For 10 points, (10[1])name this constant that multiplies concentration gradient in Fick’s first law. ■END■ (10[2])

ANSWER: diffusion coefficient [or D or mass diffusivity; accept diffusion constant; accept tracer diffusion coefficient or self-diffusion coefficient or Dc or Da; accept just diffusion after “constant” is read]
<MS, Chemistry> | NAFTA-Packet-8
= Average correct buzzpoint

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