5L O2 x 1 mol O2/ 22.4L O2 x 2 mol H20/ 1 mol O2 x 22.4L H20/ 1 mol H20 = 10 L H2O
For future reference though, since its at STP that means that the coefficient are in proportion. Since oxygen has a coefficient of 1 and water has a coefficient of 2 for every 1 liter of oxygen there is 2 liters of water. Hence you started with 5 liters and ended with 10
D.4s this would be the answer because after eight electrons are added to the third orbital two have to be added to the fourth before more can be added to the third one. The third orbital can hold 18 electrons, but it first has to have eight, then two on the fourth orbital, then the rest of the ten can be added
Here's a website with the answer and some cool reading:
http://history-world.org/archeology.htm
A proper ionic formula has a cation and an anion in it; an ionic compound is never formed between two cations only or two anions only. The key to writing proper ionic formulas is simple: the total positive charge must balance the total negative charge.
