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## Gases

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**Gases**Chapter 13**Kinetic Molecular Theory**• Gases consist of large numbers of tiny particles that are far apart relative to their size. • Collisions between gas particles and between particles and container walls are elastic collisions. • Gas particles are in continuous, rapid, random motion**4) There are no forces of attraction or repulsion between**gas particles. 5) The average kinetic energy of gas particles depends on the temperature of the gas. *This applies only to ideal gases**Diffusion-a spontaneous mixing of particles of two**substances caused by their random motion. Ex: air freshener spreading throughout a room. Effusion-process by which gas particles pass through a tiny opening. Ex: filling your tire up with air with the little needle. Pressure-force per unit area**Avogadro’s Law**Example 1 Consider two samples of nitrogen gas. Sample 1 contains 1.5mol of N2 and has a volume of 36.7L at 25°C and 1atm. Sample 2 has a volume of 16.5L at 25°C and 1atm. Calculate the number of moles of nitrogen in Sample 2.**Answer**0.67mol**V1=V2**n1 n2 n1=1.5mol 36.7 = 16.5 V1=36.7L 1.5 n V2=16.5L 36.7n=24.75 n2=? n=0.67mol T and P are constant so don’t have to include them in the formula/equation**Avogadro’s Law**Example 2 If 2.55mol of helium gas occupies a volume of 59.5L at a particular temperature and pressure, what volume does 7.83 mol of helium occupy under the same conditions?**Answer**183L**V1=V2**n1 n2 n1=2.55mol 59.5 = V V1=59.5L 2.55 7.83 n2=7.83mol 465.885=2.55V V2=? V=183L**Gas Stoichiometry**Example 3 Calculate the volume of hydrogen produced at 1.50atm and 19°C by the reaction of 26.5g of zinc with excess hydrochloric acid according to the balanced equation. Zn + 2HClZnCl2 + H2**Answer**6.5L**65 72 135 2**Zn + 2HClZnCl2 + H2 26.5g 26.5g Zn x 1mol H2= 0.407692308mol H2 65g Zn V=? PV=nRT P=1.50atm (1.50)(V)=(0.40769)(0.082)(292) T=19C+273=292K 1.50V=9.76172936 V=6.5L**Example 4**Ammonia is commonly used as a fertilizer to provide a source of nitrogen for plants. A sample of ammonia occupies a volume of 5.00L at 25°C and 15.0atm. What volume will this sample occupy at STP?**Answer**69L**V1=5.00L V2=?**T1=25⁰C+273=298K T2=0⁰C+273=273K P1=15.0atm P2=1atm *STP stands for standard temperature and pressure 15.0(5.00)=1(V) 298 273 20475=298V 69L=V**Welcome to the Gas Phase**to the tune of “Welcome to the Jungle” Guns and Roses 1987 cd#4**Verse 1**Welcome to the gas phase, it’s not all fun and games. PV=nRT, it’s enough to drive me insane. Laws of Boyle and Avogadro, and Charles, they would say. Measure volume and pressure, extrapolate to zero K.**Chorus**Gas Phase, welcome to the gas phase, PV is n,n,n,n,n,n,n,n,R,T,T,T Use it along with stoichiometry.**Verse 2**Welcome to the gas phase, where Dalton’s law rules. Calculate partial pressure, mole fraction is the clue. Kinetic theory is applied, gives speed root-mean-square. Effusion and diffusion rates, make me pull my hair.**Chorus**Gas Phase, welcome to the gas phase, PV is N,n,n,n,R,T Van der Waals’s, new equation, see.