Question

1. How much solute is needed to prepare 500mL of a 0.5M of MgSO4? Approximately how much solvent is needed to make this solution?

2. How much solute is needed to prepare 100mL of a 0.1M of H3PO4? Approximately how much solvent is needed to make this solution?

3. How much solute is needed to prepare 1.5L of a 0.2M of AgNO3? Approximately how much solvent is needed to make this solution?

4. How much solute is needed to prepare 300mL of a 2M of FeCl3? Approximately how much solvent is needed to make this solution?

5. How much solute is needed to prepare 750 mL of a 0.05M of Tris bu er? Approximately how much solvent is needed to make this solution? (Tris bu er has a FW of 121.1g)

6. How much solute is needed to prepare 250 mL of a 0.5M of KCl? Approximately how much solvent is needed to make this solution?

7. How much solute is needed to prepare 1L of a 0.25M of NaOH? Approximately how much solvent is needed to make this solution?

8. If you have a Liter of 0.5M solution of NaCl, you want to make another liter. How much NaCl would you need to make another liter of 0.5M of NaCl?

Answer 1

1. How much solute is needed to prepare 500mL of a 0.5M of MgSO4? Approximately how much solvent is needed to make this solution?

Ans :- Given, Molarity of MgSO₄ = 0.5 M

Volume of solution = 500 mL

As, Molarity = Number of moles solute/Volume of solution in L

Therefore,

Number of moles of solute i.e. MgSO₄ = Molarity of MgSO₄ x Volume of solution in L

= 0.5 M x 0.500 L

= 0.25 mol

Also, Number of moles = Mass of substance in g / Gram molar mass of substance

Therefore,

Mass of of MgSO₄ = Number of moles of of MgSO₄ x Gram molar mass of of MgSO₄

= 0.25 mol x 120.366 g/mol

= 30.0915 g

Therefore, Required mass of solute i.e. MgSO₄ = 30.0915 g

Volume of the solution or solvent = 500 mL

Mass of Solvent = Density x Volume of solution in L

= 1.00 g/mL x 500 mL

= 500 g

Therefore, mass of solvent needed = 500 g