Air at 1 atm flows at 2 m/s across the surface of a 2 inch long surface that is covered with a thin film of water. if the air and water are at 25°c and the diffusivity of water in air is 0.25 cm²/s, estimate the water mass flux for the evaporation of water at the middle of the surface, assuming laminar boundary-layer flow. is this assumption reasonable? from perry’s handbook, for air at 25°c, μ = 0.018 cp at 25°c, the vapour pressure of water is 0.46 psia. make sure to answer if the assumption is reasonable

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.

answer: -

reaction:

na + cl ⇌ nacl

balanced chemical equation:

na + 2cl ⇌ nacl2

sodium + clorine goes to form sodium chloride (table salt).

the product is nacl2.

and the reactants are na and cl.

(note: if you don’t know what ⇌ means, read below: -

⇌(double head arrow) means reversible reaction).