describe how you would prepare 250.0 mL of 0.0550 mol L-1 NH4Cl(aq)
To prepare 250.0 mL of a 0.0550 mol L-1 NH4Cl(aq) solution, follow these steps:
1. Calculate the amount of NH4Cl needed:
moles = concentration * volume
moles = 0.0550 mol L-1 * 0.2500 L
moles = 0.01375 mol
2. Convert the moles of NH4Cl to grams using its molar mass:
molar mass of NH4Cl = (1 * 14.01 g/mol) + (4 * 1.01 g/mol) + (1 * 35.45 g/mol)
molar mass of NH4Cl = 53.49 g/mol
grams = moles * molar mass
grams = 0.01375 mol * 53.49 g/mol
grams = 0.735 g (rounded to three decimal places)
3. Weigh out 0.735 grams of NH4Cl using a balance.
4. Transfer the weighed NH4Cl to a clean and dry 250.0 mL volumetric flask.
5. Add distilled water to the flask gradually, swirling gently to dissolve the NH4Cl. Continue adding water until the flask is filled to the calibration mark (250.0 mL).
6. Mix the solution thoroughly by inverting the flask a few times or stirring with a glass rod.
7. Label the flask with the concentration and compound name: "0.0550 mol L-1 NH4Cl(aq)."
You now have a 250.0 mL solution of 0.0550 mol L-1 NH4Cl(aq). Remember to handle chemicals with care and wear appropriate safety equipment.
To prepare 250.0 mL of 0.0550 mol L-1 NH4Cl(aq), follow these steps:
1. Calculate the amount of NH4Cl needed:
- Determine the molar mass of NH4Cl (ammonium chloride) by adding the atomic masses of each element: H (1.01 g/mol) + N (14.01 g/mol) + Cl (35.45 g/mol) = 53.47 g/mol.
- Calculate the number of moles needed using the concentration and volume formula: Moles = concentration × volume (in liters). In this case, Moles = 0.0550 mol L-1 × 0.250 L = 0.01375 mol.
2. Calculate the mass of NH4Cl needed:
- Multiply the number of moles by the molar mass:
Mass = moles × molar mass = 0.01375 mol × 53.47 g/mol = 0.734 g.
- Round the mass to an appropriate number of significant figures. In this case, we will keep three significant figures: 0.734 g.
3. Weigh out 0.734 g of NH4Cl using a balance. If the balance is not sensitive enough, you could weigh out a larger amount and then adjust it to exactly 0.734 g using a smaller weight.
4. Transfer the measured mass of NH4Cl into a 250.0 mL volumetric flask using a funnel or other suitable equipment.
5. Add distilled water to the flask until the level reaches the mark on the neck of the flask. This ensures that the final volume is exactly 250.0 mL.
6. Carefully mix the solution by gently swirling or inverting the flask several times to ensure proper dissolution.
7. Label the flask with the concentration, date, and any other necessary information.
Now you have prepared 250.0 mL of 0.0550 mol L-1 NH4Cl(aq). Remember to follow appropriate safety precautions when handling chemicals.