2: Solutions
Students prepare solutions from solids or stock reagents by calculating grams needed for a target molarity, using formula weight, and converting between mass concentration, percent w/v, percent v/v, and molarity.
Mass for a Target Concentration
Click to show Mass for a Target Concentration example problem
| sucrose | |
| Volume | 75.0 mL |
| Concentration | 5.0 mg/mL |
| Molecular weight | 342.30 g/mol |
| State | Solid powder at room temperature |
How many milligrams (mg) of sucrose would you need to make 75.0 mL of a 5.0 mg/mL sucrose solution?
Note: answers need to be within 1% of the correct number to be correct.
Mass for Weight/Volume Solutions
Click to show Mass for Weight/Volume Solutions example problem
| Magnesium sulfate (MgSO4) | |
| Volume | 1000 mL |
| Concentration | 3% (w/v) |
| Molecular weight | 120.37 g/mol |
| State | Solid powder at room temperature |
How many grams (g) of magnesium sulfate (MgSO4) you would need to make 1000 mL of a 3% (w/v) MgSO4 solution?
Note: answers need to be within 4% of the correct number to be correct.
Mass for Solutions Using Molarity and Molecular Weight
Click to show Mass for Solutions Using Molarity and Molecular Weight example problem
| valine | |
| Volume | 1 mL |
| Concentration | 350 mM |
| Molecular weight | 117.15 g/mol |
| State | Solid powder at room temperature |
How many milligrams (mg) of valine would you need to make 1 mL of a 350 mM valine solution?
Note: answers need to be within 3% of the correct number to be correct.
Solute Volume for Percent Volume/Volume Solutions
Click to show Solute Volume for Percent Volume/Volume Solutions example problem
| isopropyl alcohol | |
| Volume | 200 mL |
| Concentration | 8% (v/v) |
| Molecular weight | 60.10 g/mol |
| State | Liquid at room temperature |
How many milliliters (mL) of isopropyl alcohol you would need to make 200 mL of a 8% (v/v) isopropyl alcohol solution?
Note: answers need to be within 6% of the correct number to be correct.