Question

A solution is prepared by dissolving 5g HNO3 in pure water to a total volume of 1L.

a) WHat is the pH
b) What mass of strong base sodium hydroxide (NaOH) would be required to neutralize the solution?
c) If the sodium hydroxide is available as a .1M solution, what volume of the basic solution will be needed to neutralize the acid?

Answer 1

Answer:

a)1.1  b) 3.17 g c) 0.793 L

Explanation:

Balance equation for the reaction is

HNO₃ (aq) + NaOH (aq) → NaNO₃ (aq) + H₂O (l)

to calculate the pH;

we need to find the molarity of the acid HNO₃

Molarity = no moles / volume in liters

no mole = mass given / molar mass where molar mass of  HNO₃ = 63.01 g/mol

no moles = 5 / 63.01 = 0.0794 moles

molarity = 0.0794 / 1L = 0.0794 M

a) pH = - log (H⁺)  where hydrogen ion concentration is 0.0794 since 1 mole HNO₃ ionizes to 1 mole of H⁺ concentration,  0.0794 will also ionize to give 0.0794 moles

pH =  log (0.0794)⁻¹ = 1.1

b) using the equation of the reaction

63.01 g of  HNO₃ require 39.991 g of NaOH

1g will need $\frac{39.991}{63.01}$

5g will need  $\frac{39.991}{63.01}$ × 5 = 3.17 g

c) volume of 0.1M of NaOH needed = no of moles of NaOH / Molarity

no of moles of NaOH needed = 3.17 / 39.991 = 0.0793

volume need = 0.0793 / 0.1 = 0.793 L