Question 27 3.34 pts
A chemist is using a 12.3 M HCl stock solution to make 500.0 mL
of 0.613 M HCl solution. Calculate how much of the stock
solution in mL is needed by the chemist. Express your answer
with 1 decimal place.

24.9mL of the stock solution are required

Explanation:

To solve this question we have to find, as first, the moles of HCl that we need to prepare the desire solution. These moles are taken from the stock solution as follows:

Moles diluted solution:

500.0mL = 0.5000L * (0.613mol / L) = 0.3065 moles HCl

As these moles comes from the 12.3M HCl solution, the volume that we need of the stock solution is:

Volume stock solution:

0.3065 moles HCl * (1L / 12.3moles) = 0.0249L 12.3M HCl =

"standard molar enthalpy:

h2o ( liquid water ) : - 285.8 kj/mole

h2o ( water vapor ) : - 241.8 kj / mole.

δhrxn = - 241. 8 - ( - 285.8 )= -241.8 + 285.8 = 44.0

answer: 44.0 kj"