Why isn't propyne call 1-propyne, but heptene is called 3-heptene

In this chemical reaction, 325 grams of barium (ba) react completely. how many moles of lithium (li) are produced?

Diffraction is when light is bent around obstructions. which of the these observation about clouds would indicate diffraction? a) after rain storms, you can sometimes see rainbows. b) clouds are white or gray and cannot be seen through. c) on a cloudy day, the temperature tends to be cooler than a sunny day. d) the edges of dark clouds appear lighter. this

Apush or pull that moves or changes and object when to objects touch