Which reaction is a combustion?

a. fe + s8 → fes
b. h2o → h2 + o2
c. zn + hcl → zncl2 + h2
d. nacl + agno3 → nano3 + agcl
e. hbr + naoh → nabr + h2o
f. c10h8 + 12 o2 → 10 co2 + 4 h2o

A2k pendulum has a speed of 1 m/s at a height of 1/2 meter

Carbon is allowed to diffuse through a steel plate 15 mm thick. the concentrations of carbon at the two faces are 0.65 and 0.30 kg c/m^3 fe, which are maintained constant. if the preexponential and activation energy are 6.2 x 10-7 m2 /s and 80,000 j/mol, respectively, compute the temperature at which the diffusion flux is 1.43 x 10^-9 kg/m^2 -s.

Cathy is pedaling down a steep hill on her bicycle and wants to be able to coast up the next hill, which is 25 meters high, without pedaling. cathy and her bicycle have a mass of 75 kg. assuming her bicycle is 100% efficient, what would her speed have to be?