Ammonia burns in the presence of a copper catalyst to form nitrogen gas. 4nh3(g) + 3o2(g) → 2n2(g) + 6h2o(g) δh = –1267 kj. What is the enthalpy change to burn 100 g of ammonia? molar mass=17 amu.

How should the syntax in this sentence be changed, if at all? the scientists spent years analyzing the results of numerous medical studies meant to identify the cause of the disease. no change the scientists spent years looking at the results of a variety of different medical studies meant to locate the cause of the disease. the scientists spent years reviewing medical study results to find the cause of the disease. the scientists spent years studying the results of many medical studies in order to uncover the cause of the disease.

On a test the graders have a mean of 77 and a standard deviation of 8. if we can approximate the distribution of these graders by a number distribution what percent of the students. a) scores higher than 77? b) should pass the test (grades > 60)? c) should fail the test (grades < 60)?

During which phase is the least percentage of the light that hits the moon visible from earth? new moon waxing gibbous waning crescent full moon