a 22.4 l high pressure reaction vessel is charged with 0.3910 mol of iron powder and 1.20 atm of oxygen gas at standard temperature (273 k). on heating, the iron and oxygen react according to the balanced reaction below. 4fe( s) + 3o 2( g) → 2fe 2o 3( s) after the reaction vessel is cooled, and assuming the reaction goes to completion, what pressure of oxygen remains?

In the image, layer a is the topmost layer. layer c contains fossils from the precambrian era. layer b contains dinosaur fossils, and layer a contains fossils of mammals. which two statements are supported by this evidence? 1. mammals lived before the precambrian era. 2. dinosaurs and mammals existed in the precambrian era. 3. dinosaurs evolved after precambrian organisms. 4. precambrian organisms evolved after dinosaurs. 5. precambrian organisms were the first life-forms to become fossilized, according to this sample.

The graph shows the populations of two species over time. which type of symbiotic relationship does the graph represent? a. commensal b. mutualistic c. parasitic d. parent-offspring e. predator-prey

Scientists observed a rock stratum with fossil. if mollusks evolved before arthropod, where will their fossils be found.