An unknown mass of aluminum is added to HCl solution. The aluminum metal is completely dissolved in the solution and generates hydrogen gas. See the balanced equation for the gas evolution reaction: 2 Al(s) + 6 HCl(aq) ---> 2 AlCl3(aq) + 3 H2(g) The following data is collected: Mass of Al sample: unknown g Volume of gas collected 45.38 mL Barometric pressure 754.8 mmHg Temperature
Ideal and Real Gases
Ideal gases obey conditions of the general gas laws under all states of pressure and temperature. Ideal gases are also named perfect gases. The attributes of ideal gases are as follows,
Gas Laws
Gas laws describe the ways in which volume, temperature, pressure, and other conditions correlate when matter is in a gaseous state. The very first observations about the physical properties of gases was made by Robert Boyle in 1662. Later discoveries were made by Charles, Gay-Lussac, Avogadro, and others. Eventually, these observations were combined to produce the ideal gas law.
Gaseous State
It is well known that matter exists in different forms in our surroundings. There are five known states of matter, such as solids, gases, liquids, plasma and Bose-Einstein condensate. The last two are known newly in the recent days. Thus, the detailed forms of matter studied are solids, gases and liquids. The best example of a substance that is present in different states is water. It is solid ice, gaseous vapor or steam and liquid water depending on the temperature and pressure conditions. This is due to the difference in the intermolecular forces and distances. The occurrence of three different phases is due to the difference in the two major forces, the force which tends to tightly hold molecules i.e., forces of attraction and the disruptive forces obtained from the thermal energy of molecules.
An unknown mass of aluminum is added to HCl solution. The aluminum metal is completely dissolved in the solution and generates hydrogen gas. See the balanced equation for the gas evolution reaction:
2 Al(s) + 6 HCl(aq) ---> 2 AlCl3(aq) + 3 H2(g)
The following data is collected:
Mass of Al sample: unknown g
Volume of gas collected 45.38 mL
Barometric pressure 754.8 mmHg
Temperature 23.5OC
Vapor pressure of H2O at 23.5OC 21.65 mmHg
Hydrogen gas is collected over water. The reaction proceeds until all the amount of aluminum is consumed in the gas-evolution reaction (aluminum is the limiting reactant).
(a) Calculate the mole number of the hydrogen gas generated in the reaction:
- Convert the volume of the collected gas to L: 45.38 mL = ___________ L
- Calculate the pressure exerted by H2 gas (= dry hydrogen gas):
Pressure of the dry hydrogen gas
= barometric pressure −vapor pressure of H2O(g)
= 754.8 mmHg − 21.65 mmHg
= _________ mmHg
- Determine the pressure of dry hydrogen gas in atm:
__________ mmHg = ___________ atm
- Convert the temperature to kelvin unit: 23.5OC = ________ K
Use theideal gas law to calculate the mole number of hydrogen gas collected: n=PVRT
mole number of hydrogen gas collected = _____________ mol
(b) Use stoichiometry to determine the mass of Al that reacted in this experiment.
mass of Al = ____________ g
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