Question

a) A standard solution of 0.243 M NaOH was used to determine the concentration of a hydrochloric acid solution. If 46.33 mL of NaOH is needed to neutralize 10.00 mL of the acid, what is the molar concentration of the acid?

b) A 0.150 M sodium chloride solution is referred to as a physiological saline solution because it has the same concentration of salts as normal human blood. Calculate the mass of solute needed to prepare 275.0 mL of a physiological saline solution.

Answer 1

HCl + NaOH ==> NaCl + H2O
mols NaOH = M x L = ?
From the equation you can see mols HCl \= mols NaOH
Then M HCl = mols HCl/L HCl

2.
0.150M = 0.150 mols/L = (0.150*molar mass NaCl)/L = about 8.9 g NaCl/L but that's an approx and you should redo this problem more accurately.
But you don't need 1L, you need only 275.0 mL; therefore,
8.9 g NaCl x (275/1000) = ? g NaCl needed for 275 mOl.

The easier way to work it, I think, is to ask yourself how many mols you need in the new solution? That's M x L = 0.15 x 0.275 = ?
Then ? x molar mass NaCl = g NaCl.