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Gas Laws Continued. Atmospheric Pressure. Let’s calculate the amount of atmospheric pressure pressing on our bodies! Step 1: Calculate body surface area. Use this equation:. M 2 = (Ht in Cm) 0.3964 x (Wt in Kg) 0.5378 x 0.024265. Atmospheric Pressure. Conversions: 1in = 2.54 cm
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Atmospheric Pressure • Let’s calculate the amount of atmospheric pressure pressing on our bodies! • Step 1: Calculate body surface area. • Use this equation: M2 = (Ht in Cm)0.3964 x (Wt in Kg)0.5378 x 0.024265
Atmospheric Pressure • Conversions: 1in = 2.54 cm 1lb = .45 Kg • Step 2: Next convert Meters2 into Inches2. • One Meter = 39.36 Inches. • 1M2 = 1550 In2. • Step 3: Multiply your answer from step one with step two. • Step 4: Multiply your answer from step 4 by 13.0 psi (PSI in Fort Collins)
Example • Height = 69 in • 175.26 cm • Weight = 130 lbs • 59 Kg • (175.2cm)0.3964 x (59Kg)0.5378 x0.024265= 1.676 M2 • 1.676M2 x 1550 in2 = 2597.8 in2 • 2597.8in2 x 12.5psi = 32,472.5 lbs 32,500.00 Lbs
Put it into Perspective • This is the same as three full grown elephants. • This is the same as 12 Honda Civics. • This is the same as one semi-truck.
Ideal Gas Law • The Ideal Gas Law allows us to account for the number of moles of gas in a system. • The Ideal Gas Law automatically adjusts to standard temperature and pressure using the Ideal Gas Constant (R).
Ideal Gas LawPV=nRT • Pressure is proportional to temperature. (T) • Pressure is proportional to number of moles. (n) • Pressure is inversely proportional to volume. (V)
The Universal Gas Constant • R is the universal gas constant that corrects for systems not at STP. • The value of R varies depending on which units of pressure are being used. • R = 0.0821 L atm/mol K • R = 62.4L mmHg/mol K • R = 8.31 L kPa/mol K
Dalton’s Law • John Dalton (1766-1844) • At a constant volume and temperature, the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of those gases.
Dalton’s Law • Each gas exerts its own pressure as if the other gases were not there. • You can add the individual pressures of each gas to obtain the total pressure of a gas mixture. • Mathematical Expression • Ptotal=P1+P2+P3+P4…………
The “Litter Box” Equation = dRT/P • A useful version of the Ideal Gas Law involved molar mass and gas density. • If gas density (d in g/L) is known, molar mass ( in g/mol) can easily be calculated. • We call it the “litter box” equation because a kitty says “mu”, takes a “P”, and kicks “dRT” over it.
B A Volume C D Pressure Review • Which line on the graph at the left best illustrates Boyle’s Law of pressure and volume? • If you said “D”, you are correct!
B A Volume C D Temperature Review • Which line on the graph shows Charles’ Law, the relationship between temperature and volume? • If you said “A” you are correct.
Pressure B A C D Temperature Review • Which line best illustrates Gay-Lussac’s law of pressure vs. temperature? • If you said “A” again, you are correct.