Oil at 150°c flows slowly through a long, thin-walled pipe of 25-mm inner diameter. the pipe is suspended in a room for which the air temperature is 20°c and the convection coefficient at the outer tube surface is 11 w/m2·k. estimate the heat loss per unit length of tube, in w/m. assume the pipe is long and the oil flow is fully developed.
also: why do we need to assume the velocity of the oil is slow?

In a laboratory determination of the atomic weight of tin, a sample of tin is weighed in a crucible. nitric acid is added, and the reaction proceeds to give a hydrated tin(iv)oxide plus no2and h2o. the hydrated tin(iv)oxide is then heated strongly and reacts as follows: sno2.xh2o(s)sno2(s)+ xh2o(g)the sno2is finally cooled and weighed in the crucible. explain the effect on the calculated atomic weight of tin that would result from each of the following experimental errors: (a)considerable spattering occurs when the nitric acid is added to the tin.(b)the hydrated tin(iv)oxide is not heated sufficiently to change it completely to tin oxide.