After a 680 hour heat treatment at 1130°c the concentration of a is 2.9 wt% at the 3.4 mm position within metal b. at what temperature (in kelvin) must the diffusion couple need to be heated to produce this same concentration at a 1.8 mm position after 680 h? the preexponential and activation energy values for the diffusion of a in b are 2.7 × 10-5 m2/s and 257 kj/mol, respectively.

1 a

2 b

3 b

4 d

5 d

6 d

explanation:

answer;

d. are made mostly of liquid

explanation;

-the general   composition and structure planets includes; they have a thick gas and liquid layer covering a small,solid core. mostly the gases are hydrogen and helium atmosphere and layers of liquid hydrogen. for instance neptune and uranus are examples of the outer planets, they have a core covered by ice and ammonia.

-neptune's atmosphere is hydrogen and helium with a bit of methane so there is no oxygen to breath and the interior is made up of frozen water and ammonia with a rock and iron core. thus, there is no liquid water or solid surface to survive.

not too sure thinking all accelerations are pointed down