Instead of using ratios for back titrations we can also use molarities if our solutions are standardized. A 0.188g sample of antacid containing an unknown amount of triprotic base Al(OH)3 was reacted with 25.0mL of 0.101M HCl. The resulting solution was then titrated with 10.55mL of 0.132M NaOH solution. Calculate the mass percent of Al(OH)3 in the antacid sample.
This is what I have done so far:
0.025L | 0.101mol/L = 0.00252 mol HCl 0.01055 L | 0.132mol/L = 0.001393 mol NaOH 0.00252-0.001393 = 0.001127 mol HCl neutralized by antacid 3:1 ratio 0.000376 mol Al(OH)3
I am confused as to where I go from finding mols of Al(OH)3 and don't understand how to find the total to take a percent from? This is probably really dumb but I can't figure it out.
To calculate the mass percent of Al(OH)3 in the antacid sample, you need to find the mass of Al(OH)3 and divide it by the mass of the entire sample. Here's how you can proceed:
1. Calculate the molar mass of Al(OH)3:
- Al: atomic mass = 26.98 g/mol
- O: atomic mass = 16.00 g/mol
- H: atomic mass = 1.01 g/mol
Molar mass of Al(OH)3 = 26.98 + 3(1.01) + 3(16.00) = 78.00 g/mol
2. Using the number of moles you calculated, find the mass of Al(OH)3:
Mass of Al(OH)3 = moles of Al(OH)3 * molar mass of Al(OH)3
Mass of Al(OH)3 = 0.000376 mol * 78.00 g/mol
3. Calculate the mass percent of Al(OH)3 in the antacid sample:
Mass percent = (Mass of Al(OH)3 / Mass of antacid sample) * 100%
Since you're given a 0.188 g sample of antacid, you can substitute the values:
Mass percent = (0.000376 mol * 78.00 g/mol) / 0.188 g * 100%
This calculation will give you the mass percent of Al(OH)3 in the antacid sample.
To calculate the mass percent of Al(OH)3 in the antacid sample, you need to find the mass of Al(OH)3 and then divide it by the mass of the antacid sample. Here's how you can find the mass of Al(OH)3:
1. First, calculate the molar mass of Al(OH)3:
Al (26.98 g/mol) + 3x O (16.00 g/mol) + 3x H (1.01 g/mol) = 78.00 g/mol
2. Next, calculate the moles of Al(OH)3 using the ratio you mentioned:
0.000376 mol Al(OH)3
3. Then, calculate the mass of Al(OH)3:
mass = moles x molar mass
mass = 0.000376 mol x 78.00 g/mol = 0.0293 g
Now that you have the mass of Al(OH)3, you can calculate the mass percent:
4. Calculate the mass percent:
mass percent = (mass of Al(OH)3 / mass of antacid sample) x 100%
mass percent = (0.0293 g / 0.188 g) x 100% = 15.6%
Therefore, the mass percent of Al(OH)3 in the antacid sample is 15.6%.