How many milliliters of a 0.7% stock solution are required to make 2 l of 0.2% solution? how many ml of solvent will be required to carry out the dilution?

1. To solve this question, you need to equalize the mass of solute for both solution. The calculation would be:
mass of solute= volume*concentration

mass1=mass2
volume1 * concentration1 = volume2 * concentration2
volume1 * 0.7%= 2L *(1000ml/L) * 0.2%
volume1 = 2000ml * (0.2%/0.7%)
volume1= 571.429 ml

2. Since you already have the volume of stock needed, you just need to subtract it from the total solution volume to count the number of solvents needed.
new solution volume= stock volume + diluting solvent volume
2L * 2000ml/L =  571.429ml + diluting solvent volume
diluting solvent volume= 2000ml- 571.429 ml= 1428.571ml

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