How much MgSO, should be weighed out? How many molecules of MgSO4 are in the solution? How many individual atoms of solute are present? How much water should be added?

Question

51. Prepare 2 Liters of a 4 molal (be careful with the terminology - I am asking for molality, not molarity) solution of MgSO,(Magnesium Sulfate) in water. Magnesium Sulfate is a medication used to prevent seizures in a condition termed preeclampsia in pregnancy The MgSO, is the solute and water is the solvent. Use rounded numerical atomic weights instead of exact ones with decimal values.

A. How much MgSO, should be weighed out?

B. How many molecules of MgSO4 are in the solution?

C. How many individual atoms of solute are present?

D. How much water should be added?

Answer 1

A. To prepare 2 liters of a 4 molal solution of MgSO4, we need to calculate the mass of MgSO4 required.

First, we need to convert 4 mol/kg to moles per liter, since we are preparing a 2 liter solution:

4 mol/kg x 1 kg/1000 g x 120.37 g/mol = 0.48296 mol/L

Therefore, we need 0.48296 mol/L x 2 L = 0.96592 mol of MgSO4.

The molar mass of MgSO4 is 120.37 g/mol, so the mass of MgSO4 needed is:

0.96592 mol x 120.37 g/mol = 116.23 g of MgSO4

Therefore, 116.23 g of MgSO4 should be weighed out.

B. To calculate the number of molecules of MgSO4 in the solution, we need to use Avogadro's number:

0.96592 mol x 6.022 x 10^23 molecules/mol = 5.81 x 10^23 molecules of MgSO4

Therefore, there are 5.81 x 10^23 molecules of MgSO4 in the solution.

C. To calculate the number of individual atoms of solute present, we need to multiply the number of molecules by the number of atoms in each molecule.

MgSO4 contains 1 magnesium atom, 1 sulfur atom, and 4 oxygen atoms.

Therefore, there are 5.81 x 10^23 molecules x (1 + 1 + 4) = 3.487 x 10^24 individual atoms of solute present.

D. To prepare a 4 molal solution, we need to dissolve 116.23 g of MgSO4 in a total of 2 kg (2000 g) of water.

The mass of water needed can be calculated by subtracting the mass of MgSO4 from the total mass of the solution:

2000 g - 116.23 g = 1883.77 g of water

Therefore, approximately 1883.77 g (or 1.88 L) of water should be added to dissolve the MgSO4 and prepare a 4 molal solution of MgSO4 in water.