3.5 cm of Mg ribbon(0.009729 g/cm0 reacts with HCL to produce 32.6 ml. of Hydrogengas at 750 mm Hg and 20 degree C. the vapor pressure of water at 20 degree C is 17.5 mm Hg. Calculate the molar volume of hydrogen (L/mole) and the percent error in your determination
I suppose you mean the mass of Mg = 0.009729 g/cm.
Mass Mg = 0.009729g/cm x 3.5 cm = approximately 0.034g (but you can get a more accurate answer).
mols Mg = grams/molar mass = 0.034/24.3 = 0.0014 = mols H2 (from the equaton below.)
Mg + 2HCl ==> H2 + MgCl2
32.6 mL wet H2 gas at the conditions listed. Convert this to STP for DRY H2 gas. Use (P1V1/T1) = (P2V2/T2)
P1 = 750-17.5 = ?mm
V1 = 32.6 mL
T1 = 273+20 = ?
P2 = 760 mm
V2 = ?
T2 = 273
I get V2 = approximately 30 mL and that is for 0.0014 mol.
For 1 mol that will be 30/0.0014 = about 20,000 mL/mol. The recognized molar volume is 22,400 mL/mol. Your experimental error is
[(20,000 - 22,400)/(22,400)]*100 = about 6%
To calculate the molar volume of hydrogen gas and the percent error in your determination, we'll first need to determine the number of moles of hydrogen gas produced.
1. Calculate the number of moles of magnesium used:
We are given the length of magnesium ribbon and its density, so we can calculate its mass.
Mass of magnesium = Length of ribbon * Density
Mass of magnesium = 3.5 cm * 0.009729 g/cm^3
2. Calculate the number of moles of hydrogen gas produced:
According to the balanced chemical equation for the reaction between magnesium and hydrochloric acid:
Mg (s) + 2HCl (aq) -> MgCl2 (aq) + H2 (g)
We see that 1 mole of magnesium produces 1 mole of hydrogen gas. Therefore, the number of moles of hydrogen gas produced is equal to the number of moles of magnesium used.
3. Calculate the volume of hydrogen gas produced:
We are given the volume of hydrogen gas produced, but we need to adjust it for the vapor pressure of water at 20 degrees Celsius.
Corrected volume of hydrogen gas = Volume of hydrogen gas - Vapor pressure of water
Corrected volume of hydrogen gas = 32.6 ml - 17.5 mm Hg
4. Convert the corrected volume of hydrogen gas to liters:
Converting milliliters to liters, we have:
Corrected volume of hydrogen gas = 32.6 ml * (1 L / 1000 ml)
5. Convert temperature to Kelvin:
The given temperature is in degrees Celsius, but we need to convert it to Kelvin by adding 273.15.
Temperature in Kelvin = 20°C + 273.15
6. Convert pressure to atm:
The given pressure is in mm Hg, but we need to convert it to atm by dividing by 760.
Pressure in atm = 750 mm Hg / 760
7. Calculate the molar volume of hydrogen gas:
The molar volume is calculated using the ideal gas law equation:
PV = nRT
where P is the pressure, V is the volume, n is the number of moles, R is the ideal gas constant, and T is the temperature.
Molar volume of hydrogen gas = (Pressure in atm * Corrected volume in L) / (Number of moles * Temperature in Kelvin)
8. Calculate the percent error:
Percent error = ((Experimental value - Accepted value) / Accepted value) * 100
To find the accepted value for the molar volume of hydrogen gas, we can refer to the ideal gas law, at standard conditions (0°C, 1 atm), the molar volume of any ideal gas is approximately 22.4 L/mol.
Now you have all the necessary information to calculate the molar volume of hydrogen gas and the percent error in your determination using the steps outlined above.