Calculate the change in enthalpy for the following reaction: 4NH3 (g) + 7O2 (g) --> 4 NO2 (g) + 6 H20 (l)
AH NH3= -46
AH4NO2= +34
AH+H200=-286
AH reaction= kJ/mol
Is this reaction endothermic or exothermic?

Can someone me with questions 15 to 17 plz.

The diagrams show objects’ gravitational pull toward each other. which statement describes the relationship between diagram x and y? gravity attracts only larger objects toward one another. gravity attracts larger objects only if they are close to one another. if the masses of the objects increase, then the force between them also increases. if distance between the objects increases, then the amount of force also increases.

Ageologist determines that a sample of a mineral can't be scratched by a steel nail but can be scratched by a masonry drill bit. based on this information, the sample mineral has to be softer than a. orthoclase. b. fluorite. c. apatite. d. corundum.