Experimental Determination Of The Gas Constant Objectives The Objectives Of This Lab Are To Experimentally Determine The 1 (68.45 KiB) Viewed 11 times
Experimental Determination Of The Gas Constant Objectives The Objectives Of This Lab Are To Experimentally Determine The 2 (59.25 KiB) Viewed 11 times
Experimental Determination Of The Gas Constant Objectives The Objectives Of This Lab Are To Experimentally Determine The 3 (41.31 KiB) Viewed 11 times
Experimental Determination of the Gas Constant Objectives The objectives of this lab are to experimentally determine the value of the Gas Constant, R, and to practice using the Gas Laws to solve a variety of problems. Background A gas is the state of matter that is characterized by having neither a fixed shape nor a fixed volume. Gases exert pressure, are compressible, have low densities and diffuse rapidly when mixed with other gases. On a microscopic level, the molecules (or atoms) in a gas are separated by large distances and are in constant, random motion. Four measurable properties can be used to describe a gas quantitatively: pressure (P), volume (V). temperature (7) and mole quantity (n). The relationships among these properties are summarized by the Gas Laws, as shown in the table below. Charles's Law: Boyle's Law: Avogadro's Law: Combined Law: Vx T [P and n are held constant] As gas temperature increases, gas volume increases. V x 1/P [Tand n are held constant] As gas pressure increases, gas volume decreases. Von [P and T are held constant] As the number of moles of gas increase, gas volume increases. Vo T/P [n is held constant] Obtained by combining Boyle's Law and Charles's Law. KL T, T, P.V₁ = P.V₁ K_V₂ n₂ 1₂ PV. P.V. T₁ T₂ A closer look at the Combined Law reveals that the volume of a gas depends on both the pressure and temperature. Thus, if the volumes of two gases are to be compared, they must be under the same P and T. A commonly used set of P and 7 reference conditions is known as Standard Temperature and Pressure, or STP. Standard temperature is defined as exactly 0 °C (273 K) and standard pressure is defined as exactly 1 atm (760 mm Hg). The Ideal Gas Law is obtained by combining Boyle's Law, Charles's Law and Avogadro's Law together: PV = nRT Here, P represents as the gas pressure (in atmospheres); V is the gas volume (in Liters); n is the number of moles of gas in the sample; T is the gas temperature (in Kelvins). R is a proportionality constant called the Gas Constant, and has a theoretical value of 0.08206 L-atm/K-mol. Note that the units of R will allow the units of P, V, n and T' in the Ideal Gas Law to cancel correctly. Page 1 of 4
Experimental Data Experimental Determination of the Gas Constant (a) Mass of Magnesium metal used (b) Volume of H₂ gas collected (c) Temperature of H₂ gas collected (d) Atmospheric Pressure (e) Temperature of Water in bath (bucket) (f) Vapor Pressure of Water at above temperature. Trial 1 Volume of H₂ gas (in L) 31.9 MLX IL =0.0319LH₂ 1000ML Temperature of H₂ gas (in K) 24.084273.15=297-15 K Data Analysis • Using your experimental data, determine the value of R, the gas constant. Show all your conversions and calculations for each step clearly in the table below. Pay attention to units and significant figures. Trial 2 Moles of H₂ gas gximole Mimolett- гид мд = Trial 1 1023 14 31-9 242 Imole Mg Trial 2 10.0406 mg 411,2mL 768.2 mm Hg 246 22-4mm Ag 41-2 X 1L 23.02 768.2 mmille 23.08 21.1 mmitg 24 =0.041241₂ 1000m |k=232+273·15=296·15K 0.0408x L mo mg x Imolett ₂ гудия Допотему 0.0406=0.0016g mole H₂ Pressure of H₂ gas (in atm) 768.2 mmHg-Vop. pres IP-VP=pmm Hg > Atm. 4 mm Hgxlatm 760mmHg 768.2-21.1 mmHg=747.7h 21.1mg/g xatm 000 760mmily Page 1 of 2
Experimental value of R (include units) R = Pr VTT |R= PU MT 0.0398 0.50049 0.98 30X0-0412 0.00169X296.15 =0.0795 • Average value of R (include units): • Percent Error between your average value and the theoretical value of R (show work): Questions Hydrogen gas can be generated from the reaction between aluminum metal and hydrochloric acid: 2 Al(s) + 6 HCl (aq) → 2 AICI, (ag) + 3 H₂(g) 1) Suppose that 3.00 grams of Al are mixed with excess acid. If the hydrogen gas produced is directly collected into a 850. mL glass flask at 24.0 °C, what is the pressure inside the flask (in atm)? 2) This hydrogen gas is then completely transferred from the flask to a balloon. To what volume (in L) will the balloon inflate under STP conditions? 3) Suppose the balloon is released and rises up to an altitude where the temperature is 11.2 °C and the pressure is 438 mm Hg. What is the new volume of the balloon (in L)? Page 2 of 2
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