Describe how to make 100 mL of a 0.120 M solution of CU(NO3)2 * 3H20
(Making a solution lab)
How many mols do you want? That's M x L = ?
Then mols = grams/molar mass. You know mols and molar mass; solve for grams.
What you want to do is weigh out that amount of Cu(NO3)2.3H2O, place it in a 100 mL volumetric flask, add some water, swirl to dissolve all of the salt, then make up to the mark on the flask with DI H2O, and mix thoroughly. The mistake many students make is to say to add the salt to 100 mL H2O and if you do that it will be wrong. salt + 100 mL makes MORE than 100 mL volume.
To make a 100 mL solution of 0.120 M Cu(NO3)2 · 3H2O, you will need to follow these steps:
1. Determine the molar mass of Cu(NO3)2 · 3H2O:
- The molar mass of Cu is 63.55 g/mol.
- The molar mass of N is 14.01 g/mol.
- The molar mass of O is 16.00 g/mol.
- The molar mass of H is 1.01 g/mol.
Thus, the molar mass of Cu(NO3)2 · 3H2O is:
63.55 g/mol (Cu) + 2 × 14.01 g/mol (N) + 6 × 16.00 g/mol (O) + 3 × (2 × 1.01 g/mol) (H) = 241.61 g/mol.
2. Calculate the amount of Cu(NO3)2 · 3H2O needed to make the solution:
- The concentration is given as 0.120 M, which means 0.120 moles of Cu(NO3)2 · 3H2O in 1 liter of solution.
- Since you want to make a 0.100 L (100 mL) solution, you will need:
0.120 moles/L × 0.100 L = 0.012 moles of Cu(NO3)2 · 3H2O.
3. Calculate the mass of Cu(NO3)2 · 3H2O needed:
- The mass can be calculated using the molar mass and the number of moles.
- The mass of Cu(NO3)2 · 3H2O needed is:
0.012 moles × 241.61 g/mol = 2.899 g.
4. Measure 2.899 grams of Cu(NO3)2 · 3H2O using a balance.
5. Transfer the measured Cu(NO3)2 · 3H2O to a 100 mL volumetric flask.
6. Add distilled water to the flask until the volume reaches the calibration mark (100 mL). Gently swirl the flask to ensure thorough mixing.
7. Your 0.120 M Cu(NO3)2 · 3H2O solution is now ready for use.
Remember to handle chemicals and laboratory equipment with proper precautions and according to your institution's guidelines.