how we prepare a 4M solution of NaCl in 100ml and after this we dillute this 4ml solution to make3.8M solution.
How many mols NaCl do you want in the 100 mL? That's M x L = 4M x 0.1L = 0.4 mols.
How many grams is that? That's
mols = grams/molar mass. You know molar mass and mols, substitute and solve for grams. Place that amount NaCl in a 100 mL volumetric flask, add DI water, swirl until dissolved, add DI water to the mark of the flask, stopper and mix thoroughly.
Then the dilution. You made a typo; I assume that is a 4M solution not 4 mL. How much of this solution do you want? That is substituted for mL2.
mL1 x M1 = mL2 x M2
mL1 x 4M = mL2 x 3.8 M
To prepare a 4M (four molar) solution of NaCl in 100ml, you need to follow these steps:
1. Determine the amount of NaCl needed: Molarity (M) is calculated by dividing the number of moles of solute by the volume of the solution in liters. In this case, 4M indicates that there are 4 moles of NaCl in one liter of solution. So, to determine the moles of NaCl needed, you multiply the desired molarity (4M) by the volume of the solution (100ml or 0.1L):
moles of NaCl = Molarity (M) x Volume (L)
= 4M x 0.1L
= 0.4 moles of NaCl
2. Calculate the mass of NaCl needed: The molar mass of NaCl is 58.44 g/mol. To calculate the mass of NaCl required, multiply the moles of NaCl by the molar mass:
mass of NaCl = moles of NaCl x molar mass
= 0.4 moles x 58.44 g/mol
= 23.376 grams of NaCl
3. Dissolve the calculated amount of NaCl in a small volume of water: Take the 23.376 grams of NaCl and dissolve it in a small volume of water in a beaker or flask, ensuring the NaCl is completely dissolved.
4. Add distilled water to achieve a total volume of 100ml: After dissolving NaCl, transfer the solution to a 100ml volumetric flask and then add distilled water to make the total volume up to the 100ml mark on the flask.
To dilute the 4M NaCl solution to 3.8M:
1. Calculate the volume of the 4M solution needed: The dilution formula is C1V1 = C2V2, where C1 and C2 represent the initial and final concentrations, and V1 and V2 represent the initial and final volumes. Rearrange the formula to solve for V1 (volume of the initial solution):
V1 = (C2 x V2) / C1
= (3.8M x 100ml) / 4M
= 95ml of the 4M NaCl solution
2. Measure 95ml of the 4M NaCl solution: Use a graduated cylinder or pipette to carefully measure 95ml of the 4M NaCl solution.
3. Add distilled water to bring the total volume to 100ml: Transfer the measured 95ml of the 4M NaCl solution to a 100ml volumetric flask, and then add distilled water up to the 100ml mark on the flask to complete the dilution.
This will result in a final concentration of 3.8M NaCl in 100ml solution.