A 250mL sample of air at STP contains approximately 52.5mL of O2. What is the percentage of oxygen in the air

The enthalpy of formation of water is -285.8 kj/mol. what can be inferred from this statement?

Water (2510 g ) is heated until it just begins to boil. if the water absorbs 5.09×105 j of heat in the process, what was the initial temperature of the water?

13. a covalent bond between two atoms is likely to be polar if: a. one of the atoms is much more electronegative than the other. b. the two atoms are equally electronegative. c. the two atoms are of the same element. d. the bond is part of a tetrahedrally shaped molecule. e. one atom is an anion.