A 0.3120 g sample of a compound made up of aluminum and chlorine is dissolved in 150 mL H2O. When excess AgNO3 is added, 1.006 g of AgCl is precipitated. What is the number of moles Cl in the aluminum chloride sample?What is the number moles of aluminum in the sample.
I thought this was a simple question of how many molecules there are, so I put 3 for the first question and 2 for the second. Apparently that was wrong so I put 2 and 1, which is still wrong. Help?
mols AgCl = 1.006/molar mass AgCl = 0.0072.
It isn't clear in the problem if Al and Cl are combined as AlCl3 or if they are there as a mixture. In my ignorance I would go with 0.0072 mols Cl in the AlCl3 and 1/3 of that for mols Al.
Thanks, but that wasn't the right answer?
Well, i made a typo. That's 0.00702 and not 0.0072. I usually check my post immediately after I respond but I didn't on this one. Also I notice the 0.3120 and 1.006 are to four significant figures so the 0.00702 number is revised to 0.007019 mols. Mols Al in the sample HAS to be 1/3 of 0.007019. I'm still of the opinion that mols Cl = 0.007019 and mols Al = 1/3 x 0.007019.
To determine the number of moles of chlorine (Cl) and aluminum (Al) in the sample, you can use stoichiometry and the given information from the experiment.
First, let's calculate the number of moles of AgCl precipitated:
Given: Mass of AgCl = 1.006 g
To find the moles of AgCl, you need to use its molar mass. AgCl is made up of silver (Ag) and chlorine (Cl) in a 1:1 ratio. The atomic masses of Ag and Cl are 107.87 g/mol and 35.45 g/mol, respectively. Therefore, the molar mass of AgCl is:
Molar mass of AgCl = (1 mol Ag × atomic mass of Ag) + (1 mol Cl × atomic mass of Cl)
Molar mass of AgCl = (1 mol × 107.87 g/mol) + (1 mol × 35.45 g/mol)
Molar mass of AgCl = 143.32 g/mol
Now, you can calculate the number of moles of AgCl using the equation:
moles of AgCl = mass of AgCl / molar mass of AgCl
moles of AgCl = 1.006 g / 143.32 g/mol
Next, you need to determine the moles of Cl in the AgCl molecule. Since there is a 1:1 ratio between AgCl and Cl, the number of moles of Cl is the same as the number of moles of AgCl.
So, the number of moles of Cl in the aluminum chloride sample is the same as the moles of AgCl, which you calculated earlier.
Now, let's determine the number of moles of aluminum (Al) in the sample. Since we know the composition of aluminum chloride (AlCl3) and the moles of Cl (which are the same as moles of AgCl), we can find the number of moles of Al using the stoichiometry of the reaction.
According to the balanced chemical equation, the ratio of Al to Cl in aluminum chloride is 1:3. So, for every 1 mole of AlCl3, there are 3 moles of Cl.
Therefore, if the number of moles of Cl (moles of AgCl) is X, then the number of moles of Al is X/3.
To summarize:
- The number of moles of Cl in the aluminum chloride sample is moles of AgCl.
- The number of moles of Al in the sample is moles of AgCl divided by 3.
I hope this explanation helps you understand how to solve the problem.