Please help meh, quiz :)

What is the enthalpy of combustion (per mole) of c4h10 (g)? –2,657.5 kj/mol –5315.0 kj/mol –509.7 kj/mol –254.8 kj/mol

If i had 2 m naoh solution, what does the 2 m stand for? 2 molar, but 2 of a solute in 1

Select the correct location on the image identify the element that humans need to breathe. 2015 er r ights reserved