For each of the following explain how you would prepare 1.0 L of a solution that is 0.10 M in K+. Repeat for concentrations of 1.0 × 102 ppm K+ and 1.0% w/v K+.
For 0.1M K^+, you want 0.1 mol K^+/L soln.
1 mol KCl = about 74.5 g. 0.1 mol = 7.45 g KCl and that gives you 0.1 mol K^+. Therefore place 7.45 g KCl in some water, swirl until dissolved, add water to the 1 L mark, mix thoroughly.
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Yes
To prepare a 1.0 L solution that is 0.10 M in K+, you would need to follow these steps:
Step 1: Determine the molar mass of K+
The molar mass of K+ (potassium ion) is approximately 39.10 g/mol.
Step 2: Calculate the mass of K+ required
To calculate the mass of K+ needed to prepare the solution, you need to use the formula:
Mass (g) = Molarity (mol/L) x Volume (L) x Molar Mass (g/mol)
In this case, the molarity is 0.10 M and the volume is 1.0 L. Therefore, the mass of K+ required can be calculated as:
Mass (g) = 0.10 mol/L x 1.0 L x 39.10 g/mol = 3.91 g
Step 3: Weigh the potassium compound
Now, you need to weigh out 3.91 grams of a potassium compound that will provide the desired amount of K+. The choice of potassium compound depends on the available options, such as potassium chloride (KCl) or potassium nitrate (KNO3).
Step 4: Dissolve in solvent
Next, add the weighed potassium compound to a container and dissolve it completely in some solvent, such as distilled water. Stir the solution until all the solid has dissolved.
Step 5: Make the final volume
Finally, add more solvent, in this case water, to bring the total volume of the solution up to 1.0 L. Stir again to ensure proper mixing, and your 0.10 M K+ solution is now ready for use.
Repeat the same procedure for the other two concentrations:
For a concentration of 1.0 × 102 ppm K+:
Step 1: Determine the molar mass of K+, as mentioned earlier.
Step 2: Calculate the mass of K+ required:
Mass (g) = ppm concentration x Volume (L) / 10^6
In this case, the concentration is 1.0 × 10^2 ppm (parts per million) and the volume is 1.0 L. Calculating the mass of K+ gives:
Mass (g) = (1.0 × 10^2) x (1.0/10^6) = 0.0001 g = 0.1 mg
Step 3: Weigh the potassium compound, as in the previous case.
Step 4: Dissolve in solvent, as explained earlier.
Step 5: Make the final volume, as mentioned earlier.
For a concentration of 1.0% w/v K+:
Step 1: Determine the molar mass of K+, as mentioned earlier.
Step 2: Calculate the mass of K+ required:
Mass (g) = w/v concentration x Volume (mL) / 100
In this case, the concentration is 1.0% w/v (weight/volume) and the volume is 1.0 L. Calculating the mass of K+ gives:
Mass (g) = (1.0) x (1000/100) = 10 g
Step 3: Weigh the potassium compound, as in the previous cases.
Step 4: Dissolve in solvent, as explained earlier.
Step 5: Make the final volume, as mentioned earlier.
By following these steps, you can prepare 1.0 L solutions with concentrations of 0.10 M K+, 1.0 × 102 ppm K+, and 1.0% w/v K+.