Evaluation Of Gas Law Constant

2 Pages 605 Words

Evaluation of Gas Law Constant




Objective: The gas law constant, R, will be evaluated using a reaction between hydrochloric acid and a metal to produce hydrogen gas.

Procedure: In this experiment, use the reaction of a metal with hydrochloric acid to produce a known number of moles of hydrogen gas. If the volume, temperature, and pressure of the gas sample are then measured, the gas constant can be obtained by appropriate rearrangement of the Ideal Gas Law. The number of moles of gas in this reaction is equivalent to the number of moles of metal used, assuming that all of the metal is consumed. The volume of gas is calculated by water displacement in a graduated cylinder. The temperature may be obtained by recording the temperature of the water being displaced. The pressure must be corrected for the presence of water in the collected gas. See the discussion of water vapor in chapter 5 of the lecture text. The total pressure of the system is comprised of the pressure of the hydrogen gas, the pressure of the aqueous solution pushing on the gas and the pressure of water vapor also present in the collection tube. To account for the solution pushing on the gas, the height of the water in the collection tube must be measured and converted to mmHg. Divide the density of mercury (13.6 g/mL) by the density of water (1.00 g/mL) to obtain the relative density of mercury. Then divide the length of the water column remaining in the tube by the relative density to obtain the pressure on mmHg. Subtract this value from the barometric pressure (mmHg) to obtain the pressure of the wet gas in mmHg. Next subtract the vapor pressure of water at the experimental temperature, given on the table posted in the lab, from the wet gas pressure to obtain the pressure of the dry gas. Convert this value to atm for your calculation of R.

DATA
Trial 1 Trial 2
Mass of metal (g) .082g .0084g
Moles of metal (mol) .003mol .003mol
Volume of gas m...