Percent composition of (NO3)-4

What is common about these molecules? a.their atoms are held together by covalent bonds. b.they are all made up of the same two atoms. c.their atoms are held together by ionic bonds. d.they are all made up of oxygen atoms only.

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?

The diagram shows the positions of the sun, moon and earth during spring tides, when the high tides are at their highest and low tides at their lowest. what is it about these positions that causes these high and low tides?