Download Molar Volume of Hydrogen Gas Experiment: Investigating Avogadro's Hypothesis and more Study notes Law in PDF only on Docsity! Molar Volume of a Gas Name Period INTRODUCTION In this experiment the chemical significance of Avogadro's hypothesis will be investigated. Avogadro's hypothesis states equal volumes of gases under the same temperature and pressure contain equal numbers of molecules. The volume occupied by one mole of any gas at standard temperature and pressure equals 22.4 L/mol. The volume of hydrogen gas evolved in a reaction between magnesium metal and hydrochloric acid will be determined. The gas can be collected by water displacement in a gas-measuring tube. The experimental results will then be compared to the results predicted by Avogadro's hypothesis. Pre-lab 1. Write the balanced chemical equation, including states of matter, for the reaction between magnesium metal and hydrochloric acid. What gas is produced in the reaction? 2. What is the mole-ratio between magnesium and hydrogen? 3. Write the equation for Dalton’s law. 4. What must be accounted for when a gas is collected by water displacement (Hint: Think about what takes place at the surface of a liquid.)? 5. If a gas is collected by water displacement, and the water is displaced against atmospheric pressure, how would the total pressure of the gas collected over the water compare to atmospheric pressure after all of the gas was produced? 6. Write the equation for the combined gas law. 7. What is STP in Kelvin and kilopascals? EQUIPMENT 400 mL beaker 6.0 M HCl funnel 50 mL gas-measuring tube ~0.03 g of magnesium ribbon ring stand one-hole rubber stopper ~15 cm strip of copper wire thermometer utility clamp 25 mL graduated cylinder PROCEDURE 1. Fill the 400 ml beaker completely with room temperature water. Measure and record the temperature of the water. 2. Measure and record the barometric pressure of the room. 3. Obtain ~0.03 g of magnesium ribbon. Measure and record the mass of the ribbon. 4. Obtain a piece of copper wire/rubber stopper that will fit inside the gas- measuring tube and wrap the magnesium ribbon in it. (Figure 2) 5. Using a funnel, slowly pour about 10 ml of 6.0 M HCl into the gas tube. 6. Tilt the tube slightly so the air may escape and slowly fill it with room temperature water from the 400 mL beaker using a funnel. Pour the water slowly so the water and acid mix as little as possible. 7. With the tube completely full of water, insert the magnesium ribbon and copper wire/rubber stopper about 3 cm into the tube. The stopper should force water and all air bubbles out of the tube and should hold the wire suspending the magnesium ribbon in place. 8. With finger over the hole in the stopper (make sure there is no air in the hole of the stopper), invert the stoppered end of the tube in the beaker of water. Clamp the gas-measuring tube in place so that the bottom of the rubber stopper is slightly above the bottom of the beaker. The reaction will not start immediately because it takes time for the acid to diffuse down through the column of water to the metal. (Figure 1) 9. When the magnesium has reacted completely and evolution of gas has stopped, tap the tube with finger to dislodge any bubbles seen attached to the side of the tube. Allow a few minutes for the gas to stabilize to room temperature and room pressure. Then record the gas volume in the data table. DATA Room Temperature (K) Barometric Pressure (kPa) Mass of Mg Ribbon (g) Volume of H2 Gas Collected (ml) Vapor Pressure H2O (kPa) at Temperature: Look this value up! Look up the Vapor Pressure of water at the experimental temperature. You should be able to Google “Vapor Pressure of Water at ?”.
