Question:
Zinc metal is added to hydrochloric acid to generate hydrogen gas and is collected over a liquid whose vapor pressure is the same as pure water at 20.0 degrees C (18 torr). The volume of the mixture is 1.7 L and its total pressure is 0.987 atm. Determine the number of moles of hydrogen gas present in the sample.
A. 0.272 mol
B. 0.04 mol
C. 0.997 mol
D. 0.139 mol
E. 0.0681 mol
Answer:
The correct option is;
E. 0.0681 mol
Explanation:
The equation for the reaction is
Zn + HCl = H₂ + ZnCl₂
Vapor pressure of the liquid = 18 torr = 2399.803 Pa
Total pressure of gas mixture H₂ + liquid vapor = 0.987 atm
= 100007.775 Pa
Therefore, by Avogadro's law, pressure of the hydrogen gas is given by the following equation
Pressure of H₂ = 100007.775 Pa - 2399.803 Pa = 97607.972 Pa
Volume of H₂ = 1.7 L = 0.0017 m³
Temperature = 20 °C = 293.15 K
Therefore,
Therefore, the number of moles of hydrogen gas present in the sample is n ≈ 0.0681 moles.
The answer would be B) False cause a line graph only shows ''two'' variables, not three.
<span>C3H7
The unknown compound consists of only carbon and hydrogen. The oxygen comes from the air. So you need to first determine the relative moles of hydrogen and carbon that are present in the CO2 and H2O. First, look up the molar masses of Carbon, Hydrogen, and Oxygen. Then determine the molar masses of CO2 and H2O.
Carbon = 12.0107
Hydrogen = 1.00794
Oxygen = 15.999
Molar mass of CO2
1 * 12.0107 + 2 * 15.999 = 44.0087
Molar mass of H2O
2 * 1.00794 + 1 * 15.999 = 18.01488
Number of moles of CO2
22.1 g / 44.0087 g/mol = 0.502173
Number of moles of H2O
10.5 g / 18.01488 g/mol = 0.582852
Since there's 1 carbon atom per CO2 molecule, there are 0.502173 moles of carbon.
Since there's 2 hydrogen atoms per H2O molecule, there are 2 * 0.582852 = 1.165703 moles of hydrogen.
Now we need to find a simple ratio of small integers that comes close to the ratio of 0.502173 / 1.165703 = 0.43079 to determine the empirical formula.
3/7 = 0.428571, an error of only 0.002219. The next closest ratio has an error of 0.013654, over 6 times larger.
So the empirical formula is C3H7</span>
