Using 0.1M phosphate buffer, pH 7.2, prepare 25ml each of the buffer solutions with the following concentrations at pH 7.2:
1. 0.005M
2. 0.05M
3. 0.010M
I'm not sure what your problem is. This appears to be just a dilution since the pH of the initial solution is the same as the final; therefore, you aren't being asked to change the ratio of base to acid.
So for C dilute by 10; i.e., dilute 2.5 mL to 25
For B dilute the 0.1 to 0.5; i.e., 12.5 mL of the 0.1 to 25 mL total.
For A dilute B by 10.
To prepare the buffer solutions with the desired concentrations using a 0.1M phosphate buffer at pH 7.2, you'll need to perform some dilutions. The formula for dilution is:
C1V1 = C2V2
Where:
C1 = initial concentration
V1 = initial volume
C2 = final concentration
V2 = final volume
Follow these steps to prepare each buffer solution:
1. 0.005M buffer solution:
Using the dilution formula, plug in the values:
0.1M x V1 = 0.005M x 25ml
V1 = (0.005M x 25ml) / 0.1M
V1 = 1.25ml
Measure 1.25ml of the 0.1M phosphate buffer and add distilled water to a total volume of 25ml. This will give you a 0.005M phosphate buffer solution at pH 7.2
2. 0.05M buffer solution:
Using the dilution formula, plug in the values:
0.1M x V1 = 0.05M x 25ml
V1 = (0.05M x 25ml) / 0.1M
V1 = 12.5ml
Measure 12.5ml of the 0.1M phosphate buffer and add distilled water to a total volume of 25ml. This will give you a 0.05M phosphate buffer solution at pH 7.2
3. 0.010M buffer solution:
Using the dilution formula, plug in the values:
0.1M x V1 = 0.010M x 25ml
V1 = (0.010M x 25ml) / 0.1M
V1 = 2.5ml
Measure 2.5ml of the 0.1M phosphate buffer and add distilled water to a total volume of 25ml. This will give you a 0.010M phosphate buffer solution at pH 7.2
Remember to accurately measure each volume using graduated cylinders or pipettes to ensure the desired concentrations. It is also important to use distilled water to make up the final volume to avoid introducing impurities.