I did an experiment with a sand sample which contains fine metallic aluminium and I wanted to measure how much of this metallic aluminium is in the sample. I used the NaOH solution in order to let react the aluminium and collect the H2. From the H2 amount I thought I could calculate the amount of aluminium in the sample. However now I do not know how to calculate it, I probably should first calculate the MH2 (mol), then MAl (mol) and from this I could go to Mal (g). Could you help with the equations?
start with the equation for the reaction
2Al + 6H2O --> 2Al3+ + 3H2(g) + 6OH-
This is because the OH- removes the oxide coating from the Al, but the reaction is with the water.
Hence we can see that 2 moles of Al yields 3 moles of H2.
From your volume of H2 (you also need temperature and possibly pressure) you can calculate the number of moles using
PV=nRT
If you do not have the PV information then assume that one mole of H2 occupies 22.4 litres and use this to calculate the number of moles.
The number of moles of Al is then two thirds of the number of moles of H2 (from the equation).
From the number of moles of Al calculate the mass of Al from the molar mass of Al.
Thanks, are these equations correct?
M (H2 in mol)=(V(H2 in ml)/1000)/22.4)
then
M (Al in mol)=2/3V(H2 in mol)
after
M (Al in g) = M (Al in mol) x 27
I am not sure that I follow your symbols.
Let V=volume of H2 (in ml)
Number of moles of H2=
V/(22.4 L mol^-1 x 1000 ml L^-1)
Number of moles of Al =
2xV/22.4 L mol^-1 x 1000 ml L^-1 x3)
mass of Al =
2xVx27 g mol^-1/(22.4 L mol^-1 x1000 ml L^-1 x3)
Thanks a lot.
Certainly! To calculate the amount of metallic aluminum (Al) present in the sample using the volume of hydrogen gas (H2) collected, you need to follow a series of steps.
Step 1: Convert the volume of H2 gas (in liters) to the number of moles. This can be done using the ideal gas law equation:
PV = nRT
Where:
P is the pressure of the gas (in atm),
V is the volume of the gas (in liters),
n is the number of moles of gas,
R is the ideal gas constant (0.0821 L·atm/mol·K),
T is the temperature of the gas (in Kelvin).
Step 2: Determine the molar ratio between H2 and Al. This can be done by balancing the chemical equation of the reaction between Al and NaOH, which produces H2 gas.
2Al + 6NaOH → 2Na3AlO3 + 3H2
The balanced equation shows that 2 moles of Al react to produce 3 moles of H2. Therefore, the ratio is 2 moles of Al to 3 moles of H2.
Step 3: Calculate the number of moles of Al. Since you know the moles of H2 from step 1 and the molar ratio from step 2, you can use stoichiometry to find the moles of Al. Use the following equation:
Moles of Al = (moles of H2) * (2 moles of Al / 3 moles of H2)
Step 4: Convert the moles of Al to grams of Al. To convert moles to grams, you need to know the molar mass of Al, which is 26.98 g/mol. Use the following equation:
Mass of Al = (moles of Al) * (molar mass of Al)
Following these steps will allow you to calculate the amount of metallic aluminum (Al) in the sand sample.