Question

I totally forgot how to calculate molarity and all my other resources are not helping.
Molarity is mol of solute/L of solution
So I have 0.1 M of sodium thiosulfate and 0.1 M of hydrochloric acid

For a lab I put in 5 drops of sodium thiosulfate and 3 drops of hydrochloric acid.

I need to calculate the molarity of sodium thiosulfate with the equation M1V1=M2V2 (I believe the amount of drops is volume)

Would it look like this M1*8 = 0.8*8
As that doesn't look correct
Any help would be appreciated :)

Answer 1

M1V1 = M2V2
M 1 = 0.1 V1 = 5 drops
M2 = ? V2 = 8 drops (that's 3 drops + 5 drops = 8 drops)
0.1 x 5 = M2 x 8
That M1V1 = M2V2 comes in handy in many problems but for simple dilution problems like this I prefer to think it out; i.e.,
You have a solution that is 0.1 M and you dilute it with 5 drops up to a total of 8 drops. So final concentration is 0.1 x 5/8 = xxx
For the HCl the final concn is 0.1 x 3/8 = ?

Answer 2

Thank you! Really appreciate it!