Dr. Williamson’s Notes for Gases - Chemistry Educationchemed.tamu.edu/chem101/pptnotes/gas laws student 6pp 10p.pdf · Summary of Gas Laws: The Ideal Gas Law! Boyle’s Law ...
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! Definitions of standard pressure" 76 cm Hg" ______ mm Hg" ______ torr" _____ atmosphere" 101.3 kPa" 14.69 PSI
4
Manometer
Pgas = Patm
Pgas = ______ Pgas = ________
Kinetic Molecular Theory1. Gases consist of tiny particles (atoms or molecules)2. These particles are so small, compared to the
distance between them that the volume of the individual particles can be assumed to be _______ ______
3. These particles move in rapid, random, straight line motion until they collide with another particle or the walls of the container (causing ___________). The collisions are ______________.
4. There is __ force of attraction between gas particles or between the particles and the walls of the container.
5. The ______ _______ ________ of a collection of gas particles depends on the temperature of the gas and nothing else.
Charles’ Law: The Volume-Temperature Relationship; The Absolute Temperature Scale
! J.L. Gay-Lussac in 1802 from unpublished work of Jacques Charles in ~ 1780.
! Mathematical form of Charles’ law.! V ∝ T! V / T = k! V1 / T1 = k1 for one sample of a gas.! V2 / T 2 = k2 for a second sample of the gas.! _________for the same gas at the constant P.! Charles’ Law is:
! Avogadro’s Law = 1 mole of any gas at same P and T contains the same ________________ and the same ________________.
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Summary of Gas Laws: The Ideal Gas Law! Boyle’s Law – V ∝ 1/P (at constant T & n)! Charles’ Law – V ∝ T (at constant P & n)! Avogadro’s Law – V ∝ n (at constant T & P)! Combine these three laws into one statement
V ∝ ____________! Convert the proportionality into an equality
with a constant (R).V = __________
! This provides the Ideal Gas Law.__________________ (memorize this one)
! R is a proportionality constant called the universal gas constant. (R = _____________ L*atm/mol*K)
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Summary of Gas Laws: The Ideal Gas Law! R has other values if the units are changed.! R = 8.314 J/mol K
" Use this value in thermodynamics.
! R = 8.314 kg m2/s2 K mol" Use this later in this chapter for gas velocities.
! R = 8.314 dm3 kPa/K mol" This is R in all metric units.
! R = 1.987 cal/K mol" This the value of R in calories rather than J.
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Summary of Gas Laws: The Ideal Gas Law! Find the volume of 1 mol of gas at STP! PV = nRT
Diffusion and Effusion of Gases! This is a demonstration of diffusion.
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Diffusion and Effusion of Gases• The rate of effusion is inversely
proportional to the square roots of the molecular weights or densities.
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1
2
2
1
1
2
2
1
DD
RR
or
MM
RR
=
=
! Rate of N2 = 1molecule /millisec
! What is rate of H2?
! Let 1=H2 and 2 = N2
! R1 =
KE = ½ m v2
Real Gases: Deviations from Ideality! PV = nRT assumes that all points of the Kinetic
Molecular Theory are correct.! Real gases behave ideally at ordinary temperatures
and pressures.! At ___ temperatures and ____ pressures real gases
do not behave ideally. ! The reasons for the deviations from ideality are:
1. A GAS PARTICLE DOES HAVE VOLUME, SO VOLUME IS OFF. When the molecules are very close to one another, their volume is important (high pressure-low volume).
2. GAS PARTICLES DO ATTRACT, SO PRESSURE IS OFF. The molecular interactions become important as the particles slow down at low temperatures.
Mass-Volume Relationships in Reactions Involving Gases
2 mol KClO3 yields 2 mol KCl and 3 mol O22(122.6g) yields 2 (74.6g) and 3 (32.0g)
Those 3 moles of O2 can also be thought of as:
at STP
Or if T and P is known, you could solve for V using
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g)(2(s)&MnO
(s)3 O 3 + KCl 2KClO 2 2!!! →! Δ
! What volume of oxygen gas will be collected over water at 26 ˚C and 740 mm Hg when 1.60 g of potassium chlorate is heated, producing potassium chloride?
! b) Gas Law to get Volume of O2! V = nRT/P! T = 26 + 273 = 299K! P = P of water + P of oxygen! From table: at 26 ˚C vp of water = 25 mmHg)! P of oxygen =! ____ mmHg (1 atm/760 mmHg) = ____ atm
! V =€
V = nRTP
=
If 1.8 L of oxygen gas reacts with sufficient hydrogen gas at 25.0˚C and 1.0 atmospheres, how many moles of water will be formed? (Hint: balance equation first!)