Answer:
(A) 1350
Explanation:
To find the volume of 0.5 M NaOH required for the complete reaction with 150 ml of 1.5 M H₃PO₃ solution, we need to use the stoichiometry of the reaction between NaOH and H₃PO₃ and the concept of molarity.
The balanced chemical equation for the reaction between NaOH and H₃PO₃ is:
3 NaOH + H₃PO₃ → Na₃PO₄ + 3 H₂O
From the equation, we see that it takes 3 moles of NaOH to react with 1 mole of H₃PO₃.
Given that the volume of H₃PO₃ solution is 150 ml and its concentration is 1.5 M, we can calculate the number of moles of H₃PO₃:
Number of moles of H₃PO₃ = volume (in liters) × concentration
= 150 ml × (1.5 mol/L)
= 0.150 L × 1.5 mol/L
= 0.225 moles
According to the stoichiometry of the reaction, the number of moles of NaOH required will be three times the number of moles of H₃PO₃.
So, the number of moles of NaOH required = 3 × 0.225 moles
= 0.675 moles
Now, we can use the definition of molarity to find the volume of 0.5 M NaOH needed:
Volume of NaOH (in liters) = Number of moles / Concentration
= 0.675 moles / 0.5 mol/L
= 1.35 L
Finally, converting liters to milliliters:
Volume of NaOH (in ml) = 1.35 L × 1000 ml/L
= 1350 ml
So, the correct answer is option (A) 1350.