# What is the size difference between Hydrogen and Oxygen

by notsoround
Tags: hydrogen atom, oxygen
 P: 3 Hi I would like to know What the size difference ratio between Hydrogen and Oxygen gas atoms, in the form of the following question...' If i had two identically separate 1 liter containers, (one containing Hydrogen, and the other Oxygen), at the very same pounds psi, Which container has more atoms in it , and at what ratio? Great forum!! Thank you very much!
 Emeritus Sci Advisor PF Gold P: 7,337 You need to show us some of your thought processes. What do you know that might help you answer this question?
 P: 21 think about moles, and think about what you know about the avagodro's law of gases.
 P: 3 What is the size difference between Hydrogen and Oxygen Thank you for your reply, and after going over Avagodro's law and moles, i did the following 2 calculations for H2 and O2 molecules. Please confirm or oppose my results... (using grams, 1kg or 1000g) I divide by the molar mass (1.0079g/mole) to get 992.2 moles of hydrogen. I then multiply by Avagadro's number, 6.0221415x10^23. That gave me 5.975x10^26 atoms in a 1kg sample of hydrogen. -vs- O2 1000g x (1 mol/ 32 g ) x (6.022 x 10^23) = 1.92 x 10^28 molecules O2 times by 2 1.92 x 10^28 x 2 = 3.85 x 10^28 atoms in a 1kg sample of Oxygen So if my conclusions are correct... 3.85 x 10^28 atoms of O is > 5.975x10^26 atoms of H, So H atoms take up more physical space than O atoms under the same conditions, hence the Oxygen tank (from the initial question) has more actual atoms. ???
 HW Helper Thanks P: 10,781 The problem says two identical 1 liter container. Why do you think that there are 1 kg gas in each? ehild
 P: 3 Integral "You need to show us some of your thought processes. What do you know that might help you answer this question?" ------------------------------ I am brand new to this. Business is more my specialty. I am completely fascinated, and believe i have found a new passion. I really appreciate this site and all your experienced feedback. -------------------------------- ehild "The problem says two identical 1 liter container. Why do you think that there are 1 kg gas in each?" Well, the tanks and their PSI are theoretical at this point. They could be any size. I attempting to understand how to formulate this kind of calculation. As i have never done this kind of calculation. But with the right mentor('s), im a quick learner! Figuring 1 kilogram = 1.04 liters, Would my calculations make sense if i said the tanks were exactly 1.04 liters?
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 Quote by notsoround I am brand new to this. Business is more my specialty. I am completely fascinated, and believe i have found a new passion.
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 Quote by notsoround Figuring 1 kilogram = 1.04 liters, Would my calculations make sense if i said the tanks were exactly 1.04 liters?
No, liter is unit of volume, kg is unit of mass. You know how big is a one-liter bottle? If it is filled with water, the mass of water is about 1 kg. The mass contained in 1 liter volume depends on the density of the substance. The density of water is about 1kg/liter, that of a gas is of the order 1 kg/m^3, that is 0.001 kg/liter.
The difference between liquids and gases is that the molecules of a liquid touch each other, so their size determines the volume the liquid occupies. The molecules of a gas are free to move and are much farther from each other than their size.
You get the number of moles of a gas like oxygen and hydrogen in a given volume at room temperature or higher by using the ideal gas law, PV=nRT. P is the pressure, V is the volume, T is the absolute temperature, R is a constant and n is the number of moles. You see that n does not depend of the kind of the gas.

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P: 5,496
 Quote by notsoround I would like to know What the size difference ratio between Hydrogen and Oxygen gas atoms, in the form of the following question...'
I surmise that the OP may have abandoned his quest for the comparative sizes of some gaseous molecules, but if still reading, I suggest that you surf to http://ask.com and type in the question: What is the size of an oxygen molecule? You will be presented with myriad links to articles guaranteed to pique your interest.

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