Question

Describe, in detail, how to make 5.5 liters of a 2.5 molar HCl solution from a 10.5 molar HCl stock solution.

Answer 1

@tcarroll010 @whpalmer4

Answer 2

Disclaimer: it's been a while!

If we know the target is 5.5 l of 2.5 molar HCl, doesn't that mean we need \(5.5 \text{ l} * 2.5 \text{ moles}/\text{l} = 13.75\) moles of HCl in the final result? Divide that by the molarity of the stock solution to get the amount of stock solution, then add water to make 5.5 liters, no?

Answer 3

Yes!

Answer 4

Thank you :)

Answer 5

I don't recall whether you add water to acid, or acid to water, let's play it safe and say "combine with appropriate safety practices in place" :-)

Answer 6

5.5 liters of 2.5 molar HCl has 5.5 x 2.5 moles of HCl=13.75 moles
10.5 molar HCl has 10.5 moles/liter
13.75 moles/10.5=1.309 liters
Then dilute 1.309 liters of 10.5 molar HCl stock solution to 5.5 liters to obtain 5.5 liters of 2.5 molar HCl

Answer 7

Always remember ADD ACID

Answer 8

I'm an electrical engineer, I'm more concerned with remembering which end of the soldering iron to hold :-)

Answer 9

but yeah, adding acid seems to make more sense — if something goes wrong, you want the big volume of water splashing about, not the acid :-)