Anonymous
Anonymous asked in Science & MathematicsChemistry · 1 decade ago

Standard Pressure and Temperature (STP)?

what is STP? like, what is it used for and what is the whole point of it?

And how can you tell if elements are a solid, liquid or gas at STP?

Update:

wait, so the whole point of STP is used to just compare other places to a point we know?

3 Answers

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  • Anonymous
    1 decade ago
    Favorite Answer

    STP is a way of keeping measurements of temperature and pressure constant so that when different formulas called "Laws" which predict the way things behave in nature, are applied, there will be a way to find out the value of things you don't know. For instance, STP is used mostly in the Ideal Gas Law. The formula for this is PV = nRT where P is pressure, V is volume, n is the number of moles of something, R is the ideal gas constant (a number that never changes) and T is temperature. With STP, you know you are always going to be talking about how many atmospheres of pressure you have. And with temperature, you will always be talking about how many degrees on the Kelvin temperature scale you have. R never changes. So you can arrange the formula to solve for the volume in liters or for moles of a substance. (There are equivalents for atmospheres and liters and degrees Kelvin, but to be correct you would use atm, L, & K). There are other laws in chemistry that have to do with the relationships between pressure, volume and temperature and combinations of them. The Ideal Gas Law which uses STP as part of it's calculation relates volume, pressure, temperature and moles of a gas under 1 set of known conditions.

    Sometimes you can tell if something is a solid, liquid or gas by looking at the formula or what you know from personal experience. If the formula talks about oxygen, it's usually a gas and steel is usually a solid. The phases (solid, liquid and gas) of all elements can change given the right conditions which usually has to do with temperature. For example even metals melt but some take over a thousand drgrees to do so. Some even melt at minus degrees temperature. I don't know of anyone who knows the phases of every element and what it takes to make them change. The periodic table has arranged elements so that different columns or "groups" share common properties so there are groups that are gases, groups that are metals, nonmetals or combinations. Basically if you want to know what phase an element is and under what conditions, you just need to look up that particular element to find out.

  • Anonymous
    1 decade ago

    It is 298K (25 deg C) an 1 atmosphere of pressure

    Point of it is that if you do something at standard conditions it should give same results wherever you do it. Saying room temperature could be very different in a cold lab compared to a lab in a tropical country

    You can tell if something is solid liquid or gas at STP by looking at the boiling and melting points. If the boiling point is less than 25 deg C then it will be a gas. It will be a liquid if the melting point is below 25 deg and the boiling point is above 25 deg (eg in the case of water). If the melting point is over 25 deg C then it will be a solid.

    Hope this helps :o)

  • Kes
    Lv 7
    1 decade ago

    Different industries (countries?) may specify different values for STP. Because gas is compressible it is difficult to value it by the cubic foot unless the value is stated at STP. You may for example buy 1,000 cubic feet of pure nitrogen at STP but have it shipped in a very high pressurized steel bottle to save space until used in a lab, etc.

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