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What is STP in chemistry? Chemistry Gases Gas Pressure. Jun 2, The abbreviation, STP stands for standard temperature and pressure. Explanation: At standard temperature and pressure, a system is said to have a temperature of zero degrees centigrade Kelvins and the pressure equal to the atmosphere is always 1 atm.
What is its temperature? We are not given the number of moles of Hg directly, but we are given a mass. We can use the molar mass of Hg to convert to the number of moles. Pressure is given in units of millimeters of mercury. We can either convert this to atmospheres or use the value of the ideal gas constant that includes the mmHg unit. We will take the second option. Substituting into the ideal gas law,. The mmHg, L, and mol units cancel, leaving the K unit, the unit of temperature. Isolating T all by itself on one side, we get.
For a 0. The ideal gas law can also be used in stoichiometry problems. What volume of H 2 is produced at K and 1. Here we have a stoichiometry problem where we need to find the number of moles of H 2 produced. Then we can use the ideal gas law, with the given temperature and pressure, to determine the volume of gas produced. First, the number of moles of H 2 is calculated:.
Now that we know the number of moles of gas, we can use the ideal gas law to determine the volume, given the other conditions:. What pressure of HCl is generated if 3. It should be obvious by now that some physical properties of gases depend strongly on the conditions. What we need is a set of standard conditions so that properties of gases can be properly compared to each other. Standard temperature and pressure STP is defined as exactly kPa of pressure 0.
For simplicity, we will use 1 atm as standard pressure. Defining STP allows us to compare more directly the properties of gases that differ from each other. One property shared among gases is a molar volume. The molar volume is the volume of 1 mol of a gas.
At STP, the molar volume of a gas can be easily determined by using the ideal gas law:. All the units cancel except for L, the unit of volume. Note that we have not specified the identity of the gas; we have specified only that the pressure is 1 atm and the temperature is K.
This makes for a very useful approximation: any gas at STP has a volume of This molar volume makes a useful conversion factor in stoichiometry problems if the conditions are at STP. If the conditions are not at STP, a molar volume of However, if the conditions are not at STP, the combined gas law can be used to calculate the volume of the gas at STP; then the A mole of gas at STP occupies Measure ad performance.
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Anne Marie Helmenstine, Ph. Chemistry Expert. Helmenstine holds a Ph. She has taught science courses at the high school, college, and graduate levels.
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