Aballoon is first filled with 4.00 moles of hydrogen. then, 2.00 moles of oxygen are added. if the volume was initially 21 l when just the hydrogen was present, what is the volume after the oxygen is added?

What is the molar mass of potassium nitrate, kno3

What is the ph of a solution that has a hydrogen ion concentration of 1.0 * 10 -9 m?

Which statement about hf is true? it is zero for any compound in its standard state. it is positive when the bonds of the product store more energy than those of the reactants. it is negative when a compound forms from elements in their standard states. it is zero for any element that is in the liquid state.