How do i write 2.345 x 10^-4cm out of scientific notation?

How many liters of hydrogen gas will be produced at stp from the reaction of 7.179×10^23 atoms of magnesium with 54.219g of phosphoric acid (h3po4) the equation is 3mg + 2h3(> mg(po4)2+3h2

For each of the following compounds, decide whether the compound's solubility in aqueous solution changes with ph. if the solubility does change, pick the ph at which you'd expect the highest solubility. you'll find ksp data in the aleks data tab. compounds does solubility change with ph

Aroom with dimensions 7.00m×8.00m×2.50m is to be filled with pure oxygen at 22.0∘c and 1.00 atm. the molar mass of oxygen is 32.0 g/mol. how many moles noxygen of oxygen are required to fill the room? what is the mass moxygen of this oxygen?