begin{equation}
begin{array}{cccc}
partial_t C & + partial_x u C + partial_x v C = & D_x partial_{xx} C + D_y partial_{yy} C + & R(C) \
begin{Bmatrix}
text{Time rate of\
change\
of concentration\
of chemical\
component }
end{Bmatrix} & +
begin{Bmatrix}
text{ Term of advection\
of chemical component }
end{Bmatrix} & +
begin{Bmatrix}
text{ Change in\
component\
due to\
diffusion \}
end{Bmatrix} & +
begin{Bmatrix}
text{Rate of\ formation
of component - Rate of\ consumption of\ component }
end{Bmatrix}
end{array}
end{equation}