05 Determining the Molar Volume of a Gas

05 Determining the Molar Volume of a Gas - Determination of...

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Determination of the Molar Volume of a Gas Avogadro’s law states that equal volumes of gases contain an equal number of molecules under the same conditions of temperature and pressure. It follows, therefore, that all gas samples containing the same number of molecules will occupy the same volume if the temperature and pressure are kept constant. The volume occupied by one mole of a gas is called the molar volume . In this experiment, you will determine the molar volume of the gas produced by the chemical reaction shown below. Mg( s ) + 2 HCl( aq ) MgCl 2 ( aq ) + H 2 ( g ) You will react a known mass of solid magnesium with an excess of hydrochloric acid, in a sealed vessel, and use the pressure change to calculate molar volume at STP. OBJECTIVES In this experiment, you will Measure the gas production of a chemical reaction by a pressure change. Determine the molar volume of the gas produced in the reaction. Calculate the molar volume of a gas at STP. Figure 1 MATERIALS Data Collection Mechanism 3.0 M hydrochloric acid, HCl, solution (5 mL per trial) sand paper or steel wool for polishing Mg ribbon small beaker for HCl solution Gas Pressure Sensor ruler (if analytical balance is not available) Temperature Probe 125 mL Erlenmeyer flask 600 mL or one liter beaker 20 mL gas syringe 10 mL graduated cylinder plastic tubing with two Luer-lock connectors magnesium ribbon, pre-cut (one approx. 15 mm piece per trial) rubber stopper assembly with two-way valve Adapted from Advanced Chemistry with Vernier & Laboratory Experiments for Advanced Placement Chemistry by Sally Ann Vonderbrink, Ph. D.
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The Determination of the Molar Volume of a Gas PROCEDURE 1. Obtain and wear goggles. Obtain the 125 mL Erlenmeyer flask that you will use for the experiment. Determine and record the available volume of the flask that the hydrogen gas will occupy as it is produced from the reaction of the solid magnesium and the hydrochloric acid solution. Account for the following items when you determine the volume of your flask: A 125 mL flask does not have a volume of precisely 125 mL. During the experiment, you will seal the flask with a rubber stopper and the stopper will occupy some of the volume of the flask. You will add 5 mL of solution (3.0 M HCl solution) to the flask. 2. Obtain a piece of magnesium ribbon. Use a piece of sandpaper or steel wool to polish it until it is silver and shiny. Measure its mass on the analytical balance. If one is unavailable, then measure and record its length to the nearest mm. Ask your instructor for the mass of one meter of polished magnesium ribbon, and record this information. Use a simple proportion to calculate the mass of your sample of Mg ribbon and record its value. Place the piece of magnesium ribbon in a clean and dry 125 mL Erlenmeyer flask.
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  • Fall '15
  • Lihs
  • Mole, Erlenmeyer flask, Sally Ann Vonderbrink

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