The law of states that in all samples of the same chemical compound, the masses of the elements are always in the same proportions.
a. not listed
b. indefinite proportions
c. conservation of energy
d. definite proportions

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catya your not at all which answer i've seen you do this on another question!

answer: semi-infinite solid initially at a uniform temperature of 400 ◦c is cooled at its surface by convection. the cooling fluid at a constant temperature of 200 ◦c has a convective coefficient (ha) of 250 w/m2.k. the physical properties of the solid: k = 20 w/m.k and α = 4 * 10-5  m2/s. using δx = 0.04 m and δt = 10 s. write the finite difference equations describing the transient heat transfer of the first five δx and the temperature profile after 30 s.