Question

A series of five calibration standards 25, 50, 75 and 100 mg/L Potassium is required to be made from a 1000mg/L Potassium standard solution. If the final volume of the calibration standards is 100 mL, what is the required volume of the 1000 mg/L Potassium standard solution?

Answer 1

Answer : The volume required is, 25 mL

Explanation :

First we have to determine the mass of potassium present in 100 mL or 0.1 L of each standards.

For 25 mg/L :

As, 1 L volume has mass of potassium = 25 mg

So, 0.1 L volume has mass of potassium = $0.1\times 25=2.5mg$

For 50 mg/L :

As, 1 L volume has mass of potassium = 50 mg

So, 0.1 L volume has mass of potassium = $0.1\times 50=5.0mg$

For 75 mg/L :

As, 1 L volume has mass of potassium = 75 mg

So, 0.1 L volume has mass of potassium = $0.1\times 75=7.5mg$

For 100 mg/L :

As, 1 L volume has mass of potassium = 100 mg

So, 0.1 L volume has mass of potassium = $0.1\times 100=10mg$

Now we have to determine the total mass of potassium.

Total mass of potassium = 2.5 + 5.0 + 7.5 + 10 = 25 mg

Now we have to determine the required volume of the 1000 mg/L Potassium standard solution.

As, 1000 mg mass of potassium present in 1 L volume

So, 25 mg mass of potassium present in $\frac{25}{1000}=0.025L$ volume

Volume required = 0.025 L = 25 mL     (conversion used : 1 L = 1000 mL)

Therefore, the volume required is, 25 mL