c) Now make up 500 mL of a 0.025M phosphate buffer using the 0.1M phosphate buffer. Show all your workings. The 0.1M is made of 120.1ml conjugate base and 379.9ml acid.
To make 500 mL of a 0.025M phosphate buffer using a 0.1M phosphate buffer, you will need to dilute the 0.1M solution to achieve the desired concentration.
Let's calculate the volumes of the acid and conjugate base needed to make the buffer.
Step 1: Calculate the moles of the final buffer solution needed.
moles = concentration × volume
moles = 0.025 mol/L × 0.5 L
moles = 0.0125 mol
Step 2: Use the mole ratio to determine the volumes of the acid and conjugate base required.
The mole ratio of the acid to the conjugate base in the 0.1M solution is 1:3. Therefore, for every 1 mol of acid, you will need 3 mol of conjugate base to make the 0.025M buffer.
moles of acid = 0.0125 mol
moles of conjugate base = 3 × moles of acid
moles of conjugate base = 3 × 0.0125 mol
moles of conjugate base = 0.0375 mol
Step 3: Convert moles to volume using the molarity and the given volumes in the 0.1M solution.
volume of acid = (mol of acid / molarity of acid) × 1000 mL
volume of acid = (0.0125 mol / 0.1 mol/L) × 1000 mL
volume of acid = 125 mL
volume of conjugate base = (mol of conjugate base / molarity of conjugate base) × 1000 mL
volume of conjugate base = (0.0375 mol / 0.1 mol/L) × 1000 mL
volume of conjugate base = 375 mL
Therefore, to make a 500 mL 0.025M phosphate buffer solution, you need 125 mL of the 0.1M acid and 375 mL of the 0.1M conjugate base.
To make 500 mL of a 0.025M phosphate buffer using the 0.1M phosphate buffer, you need to calculate the volumes of the conjugate base (CB) and acid that are required.
First, let's determine the amount of moles (M) of the desired phosphate buffer. The molarity (M) is given as 0.025M, and the total volume is 500 mL. To find the moles, we use the formula:
moles = M x V
moles = 0.025M x 0.5 L (recall that 500 mL is equal to 0.5 L)
moles = 0.0125 moles phosphate buffer
The 0.1M phosphate buffer is composed of 120.1 mL of CB and 379.9 mL of acid. To find the volumes of CB and acid needed, we need to compare their concentrations (M) and moles.
1 mL of 0.1M phosphate buffer contains 0.1 moles / 1000 mL = 0.0001 moles.
Thus, 120.1 mL x 0.0001 moles/mL = 0.01201 moles of CB.
Similarly, 1 mL of 0.1M phosphate buffer contains 0.1 moles / 1000 mL = 0.0001 moles.
Thus, 379.9 mL x 0.0001 moles/mL = 0.03799 moles of acid.
Now we need to determine the volumes of CB and acid necessary to obtain the required 0.0125 moles of phosphate buffer.
To calculate the volume of CB:
CB volume = (CB moles needed / CB concentration) x 1000 mL
CB volume = (0.0125 moles / 0.01201 moles/mL) x 1000 mL
CB volume ≈ 1,040.80 mL ≈ 1,041 mL (rounded to three significant figures)
To calculate the volume of acid:
Acid volume = (acid moles needed / acid concentration) x 1000 mL
Acid volume = (0.0125 moles / 0.03799 moles/mL) x 1000 mL
Acid volume ≈ 329.08 mL ≈ 329 mL (rounded to three significant figures)
Therefore, to make 500 mL of a 0.025M phosphate buffer using the 0.1M phosphate buffer, you will need approximately 1,041 mL of the conjugate base (CB) and 329 mL of the acid.