1. Calculate the Amount of Concentrated H2SO4 Needed

Determine the volume of concentrated H2SO4 (18.4 M) required to prepare 1 L of the 1.25% H2SO4 solution.

M1V1 = M2V2,

where M1 and V1 represent the molarity and volume of the concentrated H2SO4, M2 is the desired molarity (1.25%), and V2 is the final volume of the solution (1 L).

Rearranging the formula to solve for V1, we get:

V1 = (M2 x V2) / M1

Substituting the values:

V1 = (0.0125 mol/L x 1 L) / 18.4 mol/L = 0.0006842 L or 0.6842 mL

Therefore, you will need approximately 0.6842 mL of concentrated H2SO4 to prepare 1 L of 1.25% H2SO4 solution.

2. Prepare the Solution

- Wear appropriate safety gear, such as gloves and eye protection.

- Slowly add the calculated volume of concentrated H2SO4 (0.6842 mL) to a small beaker containing a few milliliters of distilled water.

- Swirl the beaker gently to mix the acid and water.

- Transfer the diluted acid solution to a 1 L volumetric flask.

- Rinse the beaker with a small amount of distilled water and transfer the rinsings to the volumetric flask.

- Add more distilled water to the flask until the solution reaches the 1 L mark.

- Mix the solution thoroughly by swirling the flask.

Your 1.25% H2SO4 solution is now ready for use.

Note: Always handle concentrated sulfuric acid with extreme caution, as it is a highly corrosive substance. Always slowly add acid to water, never the other way around, to avoid vigorous reactions.