Question

one has been supplied with 20mL of a 3.5M NaOH solution. If one requires a 0.35M NaOH solution, what volume of a diluent would be need to be added to the provided sample?

Answer 1

Did you try what I told you?

Answer 2

i have and im not understanding it

Answer 3

The formula is based on the concept that the number of moles for a solution doesn't change as long as no element concerned is added nor removed. So no matter what the volume is(how much water you put), the number of moles remains constant: n=mV

So you want to dilute it by adding diluent. After adding that, the number of moles must remain the same. So mV before must equal mV after. Makes sense?

Answer 4

we've never used Mv or anything in our class
we;ve used c1v1

Answer 5

thats what i'm having problems with, what numbers do i plug int together to get my answer or by which number do i divide i've tried it multiple times and my answer doesn't come up to 180mL

Answer 6

Alright then use that one. It's just a difference in notation.

Try listing what the molarity before and after dilution, and volume before dilution.

Answer 7

that's listed in the question i wrote

Answer 8

Yeah but can you pick out which is which?

Answer 9

nope because that isn't stated in the question

Answer 10

So that's where you're having problems. Ok tell me what you understand from the question.

Answer 11

20mL is my stock
the molarity is 3.5M

Answer 12

but if you need to get 0.35M how would you get it

Answer 13

and the final answer to this question is 180mL

Answer 14

So 20 mL and 3.5 are value for before. You want to get 0.35 M after dilution. Can you put that into the equation c1V1=c2V2 now?

Answer 15

ok

Answer 16

than

Answer 17

You will end up with V2 as an unknown. Solve for V2 which is the volume of the final solution you should have.

Answer 18

which is?

Answer 19

24.5?

Answer 20

Nope. Rearranged that will be V2=c1V1/c2