Question

If you have an inital molarity of .0024M of CrO4, you get 1.00mL of it, and you dilute it to the 100mL mark with 0.25M NaNO3, what is the end concnetration of your CrO4?

Answer 1

We need to apply dilution law, which is based on the mass conservation principle

initial mass = final mass

this apply for moles as weel ( if there is no reaction, which is the case )

mol of A initially = mol of A finally

or, for this case

moles of A in stock = moles of A in diluted solution

Recall that

mol of A = Molarity of A * Volume of A

then

moles of A in stock = moles of A in diluted solution

Molarity of A in stock * Volume of A in stock = Molarity of A in diluted solution* Volume of A in diluted solution

Now, substitute known data

M1*V1 = M2V2

0.0024 * 1 = M2 * (100+1)

M2 = 0.0024 * 1 /(100+1)

M = 0.000023762 for CrO4-2