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15.1-Kintic-Theory--Pressure-and-Moles

kinetic theory of gasses

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15.1-Kintic-Theory--Pressure-and-Moles

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  1. Chapter 15: Ideal Gases 15.1 Pressure, Kinetic Theory and Moles

  2. States of Matter - Gases On Mini-whiteboards describe the molecular structure of a gas including a diagram and description of the motion of particles.

  3. Pressure - Reminder Pressure is force per unit area Usually measured in Pascals (Pa) which are equivalent to Nm-2 Atmospheric pressure is 101kPa. Estimate the total force acting over the surface of your body due to air pressure. Taking the mass of an elephant as 2500kg. The weight of how many elephants is equivalent to the force created by air pressure on your body.

  4. Pressure - Reminder Pressure is force per unit area Usually measured in Pascals (Pa) which are equivalent to Nm-2 Can also be measure in: Bar: 1 Bar = 100,000 Pa mmHg: The height of a mercury column (Hg) that the pressure could support 101kPa = 760mmHg atm: Atmospheres where 1 atm = 101kPa

  5. Pressure If atmospheric pressure is 101kPa, estimate the total force that the air around you is exerting on your skin. Why don’t we notice this force?

  6. Gas and Pressure Torricelli's Experiment (1643)

  7. Magdeburg hemispheres (1654)

  8. Brownian Motion

  9. Kinetic theory views all matter as consisting of individual particles in continuous motion in an attempt to relate the macroscopic behaviors of the substance to the behavior of its microscopic particles. Kinetic model of an ideal gas

  10. Kinetic Theory of an Ideal Gas: Five assumptions • Negligible intermolecular forces except during collisions. • Volume occupied by gas molecules is negligible when compared to the volume of the container. • The time of collision is negligible compared to the time between collisions. This implies that collisions are instantaneous. • A molecule moves with uniform velocity between collisions. • All collisions are perfectly elastic.

  11. Kinetic Theory and Pressure Gas pressure is the force per unit area the gas exerts normally (at right angles) on a surface. The units are Pascals (Pa, equivalent to Nm-2). • Gas pressure is a result of the motion and repeated impacts of the huge number of particles in the gas.

  12. Avogadro's constant Avogadro Constant NA is the number of atoms in exactly 12g of the carbon isotope 12C. NA = 6.023 x 1023particles mol-1

  13. The mole A fundamental unit to measure the quantity of particles in a substance. 1 mole of any substance has the same number of particles as Avagadro’s constant NA = 6.02x1023Molecules·mol-1 N = n x NA

  14. Molar mass: the mass of one mole of a substance. As a general rule, the molar mass in grams of an element is numerically equal to its mass number Determining molar mass of a molecule: Determine the molar mass of each element, and multiply by the subscript (if there is one) Add together the molar mass for each element in the compound to obtain a molecular molar mass e.g. molar mass of water (H2O) = 2 + 8 = 10g

  15. We can make an analogy between moles and bags of sugar. It is usually more convenient to talk about the number of bags (moles) of sugar we need rather than the number of grains. In this analogy what is equivalent to: Avagadro’s constant? Molar mass? Molecular mass? How would work out the number of grains in n bags of sugar? How does the mass of one grain relate to the mass of a bag of sugar?

  16. We can make an analogy between moles and bags of sugar. We can extend this analogy by considering things other than sugar such as a sack of wheat. The number of grains would have to be the same but the mass of each grain and the whole sack will be different.

  17. 7 g a) 1 Mole ofHas a mass of b) 2 Moles of Has a mass of C) how atoms are in 8 grams of helium (mass number = 4)? 54 g 8 g/ 4 = 2 moles 2 moles x NA = 1.20 x 1024 atoms

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