Taking into account the definition of molarity and the stoichiometry of the reaction, the correct option is option C) 0.44 L of 6.9 M NaOH is needed to completely titrate 0.42 L of 2.39 M phosphoric acid.
The balanced reaction is:
H₃PO₄ (aq) + 3 NaOH (aq) → Na₃PO₄ (aq) + 3 H₂O(aq)
Then, by stoichiometry of the reaction (that is, the relationship between the amount of reagents and products in a chemical reaction), the following amounts of moles of each compound participate in the reaction:
- H₃PO₄: 1 mole
- NaOH: 3 moles
- Na₃PO₄: 1 mole
- H₂O: 3 moles
Molarity is the number of moles of solute that are dissolved in a given volume.
Molarity is determined by:
[tex]Molarity=\frac{number of moles of solute}{volume}[/tex]
Molarity is expressed in units [tex]\frac{moles}{liter}[/tex].
In this case, 0.42 L of 2.39 M phosphoric acid reacts. So, by definition of molarity, the number of moles that participate in the reaction is calculated as:
[tex]2.39 \frac{moles}{liter}=\frac{number of moles of phosphiric acid}{0.42 liters}[/tex]
Solving:
number of moles of phosphiric acid= 2.39 [tex]\frac{moles}{liter}[/tex]* 0.42 liters
number of moles of phosphiric acid= 1.0038 moles ≅ 1 mole
Approaching 1 mole of the amount of phosphoric acid required, then by stoichiometry of the reaction, 3 moles of NaOH are necessary to react with 1 mole of the acid.
Then by definition of molarity and knowing that 6.9 M NaOH is needed, you can calculate the necessary volume amount of NaOH by:
[tex]6.9 \frac{moles}{liter} =\frac{3 moles}{volume}[/tex]
Solving:
6.9 [tex]\frac{moles}{liter}[/tex]* volume= 3 moles
[tex]volume=\frac{3 moles}{6.9\frac{moles}{liter} }[/tex]
volume= 0.44 L
The correct option is option C) 0.44 L of 6.9 M NaOH is needed to completely titrate 0.42 L of 2.39 M phosphoric acid.
Learn more about molarity with this example: https://brainly.com/question/15406534?referrer=searchResults
