Fall 2012 Application of Gas Laws: Determination of the Universal Gas Constant (R) Done By Group Members: Haifa H. AlBaoud 200801318 Ola M. AlShamlan 200800179 Hessa J. AlZamil200800880

Gas Constant The Gas Constant is the proportionality constant in the equation for the Ideal Gas Law: PV = n RT Where P is pressure, V is volume, n is number of moles, and T is temperature.

Gas Constant Hydrogen (H2) Gas has properties nearly like an ideal gas. It can be made by dissolving magnesium metal in dilute hydrochloric acid: Mg(s)+2H+(aq)+2Cl- Mg2+(aq)+H2(g)+2Cl-

Gas Constant Hydrogen (H2) Gas can be collected by the displacement of water technique.

Gas Constant Things you need to know to calculate hydrogen gas by using displacement water technique: Know the mass of the magnesium to calculate the number of moles of hydrogen gas produced. The gas pressure inside the buret equal to the atmospheric pressure, when water level inside and outside buret are equal. Gas inside the burette is a mixture of hydrogen and water vapor (wet hydrogen gas).

Calculations To calculate gas constant (R): Change the measurements units to the units you want R to have. Hydrogen Pressure=atmospheric pressure – vapor pressure of water. Temperature measures with a thermometer. Volume measured by the scale on the buret Then Calculate R

Protocol Attain a strip of Mg metal, and weigh it on the electric weighing scale. Look up the atomic mass of Mg and calculate the number of moles of Mg strip. (The mass of Mg metal should be between 0.0410 and 0.0750 g.) Use this and balance chemical equation to calculate the number of moles of hydrogen produced by the reaction between Mg and excess dilute hydrochloric acid.   .

Protocol 2. Fill an 800 ml beaker with about 700 ml water. 3. Pour 10 ml of 6 M HC1 into the buret Carefully, with a minimum of mixing, add distilled water until the buret is full.

Protocol

Protocol 4. Fold the metal strip in the middle at a right angle. Place it in the burette to a depth of at least 5 cm using a clean glass rod to push it down. The strip acts as spring against the sides of the burette. If necessary, add more distilled water to raise the level to the top of the burette again

Protocol 5. Place your thump (or finger) over the top of the burette. Turn the burette over and set in in the beaker. Remove your thump only after the mouth of the burette is under water (figure1). Caution: No air should enter the burette.

Protocol 6. The density of 6 M hydrochloric acid is greater than water. So, it will sink to the bottom of the burette. When it reaches the Mg, a reaction will begin and hydrogen gas will evolve. After the reaction is complete, adjust the position of the burette until the water levels inside and outside the burette is equal. Read the level of water in the burette to the nearest 0.05 ml. The total gas pressure( hydrogen+ water vapor) in the burette is equal to atmospheric pressure under these conditions.

Protocol

Protocol

Protocol Measure the temperature of the water in the beaker .

Protocol 8. Change the units of V, T and P so that they are consistent with desired units of R & Calculate R.

Protocol

This Project Done By: Haifa H. AlBaoud 200801318 Ola M. AlShamlan 200800179 Hessa J. AlZamil200800880