Answer to Question #192293 in Organic Chemistry for GHOST

Question

a. A 25 cm³ sample of an aqueous solution of barium hydroxide, of concentration 0.146 mol dm³ was exactly neutralized by 28.7cm³ of aqueous nitric acid, according to the unbalanced equation:

Ba (OH)_2 (aq) + HNO_3(aq) ˗˗˗˗˗˗˗˗˃ Ba(NO₃)_2 (aq) + H₂O _(l)

i. Calculate the amount of nitric acid in terms molarity and in terms of number of moles 

ii. Differentiate molarity and number of moles.

Answer 1

$Moles of Ba(OH)_2 =0.146×\frac{25}{1000}=0.00365 mol$

$Moles of HNO_3=0.00365×2=0.0073mol$

Molarity of HNO_3= $\frac{0.0073}{28.7×10^{-3}}=0.25MHNO _3$

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The primary difference between the two comes down to mass versus volume. The molality describes the moles of a solute in relation to the mass of a solvent, while the molarity is concerned with the moles of a solute in relation to the volume of a solution.