The formula for epson salts is MgSO4*7H2O. If 1.250 g of the compound is dissolved in water, calculate the number of milliliters of 0.200 M Ba(NO3)2 that would be required to precipitate all of the sulfate ions as barium sulfate. Make the same determination for 1.000 g of alum.
I don't understand where to even start with this problem. Please help me.
I figured out the first part but don't understand the second part still. I looked at the response you had for someone else, but still couldn't get the right answer.
To solve this problem, we need to use the concept of stoichiometry, which allows us to relate the amounts of different substances in a chemical reaction. Here's how to approach the problem step by step:
Step 1: Calculate the number of moles of MgSO4*7H2O in 1.250 g.
The molar mass of MgSO4*7H2O can be calculated by summing the atomic masses of all its constituent atoms:
MgSO4*7H2O:
Molar mass of Mg = 24.31 g/mol
Molar mass of S = 32.07 g/mol
Molar mass of O = 16.00 g/mol
Molar mass of H = 1.01 g/mol
So, the molar mass of MgSO4*7H2O is:
(24.31 g/mol) + (32.07 g/mol) + (4 * 16.00 g/mol) + (7 * 2 * 1.01 g/mol) = 246.48 g/mol
The number of moles of MgSO4*7H2O can be calculated using the formula:
moles = mass / molar mass
So, moles of MgSO4*7H2O = 1.250 g / 246.48 g/mol
Step 2: Calculate the number of moles of sulfate ions (SO4^2-) present in 1.250 g of MgSO4*7H2O.
The MgSO4*7H2O formula indicates that there is one sulfate ion (SO4^2-) for every MgSO4 molecule. Therefore, the number of moles of sulfate ions is the same as the number of moles of MgSO4.
Step 3: Calculate the volume of 0.200 M Ba(NO3)2 required to react with all the sulfate ions.
The balanced chemical equation for the reaction between sulfate ions and barium ions (from Ba(NO3)2) is:
Ba(NO3)2 + MgSO4 → BaSO4 + Mg(NO3)2
From the equation, we can see that 1 mole of Ba(NO3)2 reacts with 1 mole SO4^2-. Thus, the number of moles of Ba(NO3)2 required is equal to the number of moles of sulfate ions.
Step 4: Calculate the volume of 0.200 M Ba(NO3)2 needed by using its molarity and the number of moles.
The volume of 0.200 M Ba(NO3)2 can be calculated using the formula:
volume = moles / molarity
So, volume of 0.200 M Ba(NO3)2 = moles of Ba(NO3)2 / 0.200 M
Repeat the same steps for 1.000 g of alum (Al2(SO4)3*18H2O) to find the volume of 0.200 M Ba(NO3)2 needed.
Remember to convert g to moles by dividing g by molar mass, and don't forget to consider the stoichiometric ratio from the balanced chemical equation.
I hope this helps! Let me know if you have any further questions.