Which of the following is the best example of a symbiotic relationship? Certain breeds of fish will often clean bigger fish. The cleaner fish gets food, the bigger fish gets a cleaning.
or
A foolish man decides to go swimming in shark-infested waters. As a result, he is bitten by a shark looking for food.
or
A pair of birds fight over a piece of food. The dominant bird wins.
or
The climate changes. As a result, hundreds of species become extinct and the land turns into a desert.
?

Aluminum–lithium (al-li) alloys have been developed by the aircraft industry to reduce the weight and improve the performance of its aircraft. a commercial aircraft skin material having a density of 2.47 g/cm3 is desired. compute the concentration of li (in wt%) that is required.

Which of the following elements would you expect to have the lowest ionization energy value? fluorine, lithium, neon, nitrogen

A3.37-mg sample of protein was chemically digested to convert its nitrogen into ammonia and then diluted to 100.0 ml. then 10.0 ml of this solution was placed in a 50-ml volumetric flask and treated with 5 ml of phenol solution plus 2 ml of sodium hypochlorite solution. the sample was diluted to 50.0 ml, and the absorbance at 625 nm was measured in a 1.00-cm cuvette and found to be 0.486. for reference, a standard solution was prepared from 10.0 mg of nh4cl (molar mass = 53.49 grams/mole) dissolved in 1.00 l of water. then 10.0 ml of this standard was placed in a 50-ml volumetric flask, treated in the same manner as the unknown, and the absorbance found to be 0.323. finally, a reagent blank was prepared using distilled water in place of unknown, it was treated in the same manner as the unknown, and the absorbance found to be 0.076. calculate the weight percent of nitrogen in the protein.