Suppose a deep sea diver dives from the surface to 81 feet below the surface. He then dives down 13 more feet. Find and interpret the sum to describe the diver's present depth.

7. what temperature is need to just dissolve 50 g of nh4cl in 75 g of water? '

The blackbody curve for a star name zeta is shown below. what is the peak wavelength for this star ?

Given the following at 25c calculate delta hf for hcn (g) at 25c. 2nh3 (g) +3o2 (g) + 2ch4 (g) > 2hcn (g) + 6h2o (g) delta h rxn= -870.8 kj. delta hf=-80.3 kj/mol for nh3 (g), -74.6 kj/mol for ch4, and -241.8 kj/mol for h2o (g)