The equivalent weight of phosphoric acid (H3PO4) in the reaction, NaOH + H3PO4 → NaH2PO4 + H2O is:
Understand the Problem
The question is asking for the equivalent weight of phosphoric acid (H3PO4) in a specific chemical reaction involving sodium hydroxide (NaOH). To solve it, we need to identify the number of hydrogen ions (H+) released by phosphoric acid in the reaction and calculate the equivalent weight based on its molar mass and the number of equivalents.
Answer
The equivalent weight of phosphoric acid in the reaction is $98 \text{ g/equiv}$.
Answer for screen readers
The equivalent weight of phosphoric acid (H₃PO₄) in the given reaction is $98 \text{ g/equiv}$.
Steps to Solve
- Identify the number of protons transferred
In the reaction, phosphoric acid (H₃PO₄) acts as an acid and donates hydrogen ions (H⁺). Here, it donates 1 H⁺ to form NaH₂PO₄.
- Determine the molar mass of phosphoric acid
The molar mass of H₃PO₄ can be calculated as follows:
- Hydrogen (H): 3 atoms × 1 g/mol = 3 g/mol
- Phosphorus (P): 1 atom × 31 g/mol = 31 g/mol
- Oxygen (O): 4 atoms × 16 g/mol = 64 g/mol
Adding these together gives:
$$ \text{Molar Mass of } H₃PO₄ = 3 + 31 + 64 = 98 \text{ g/mol} $$
- Calculate the equivalent weight
The equivalent weight is calculated using the formula:
$$ \text{Equivalent Weight} = \frac{\text{Molar Mass}}{\text{Number of H+ ions contributed}} $$
Since H₃PO₄ donates 1 H⁺ in this reaction:
$$ \text{Equivalent Weight} = \frac{98 \text{ g/mol}}{1} = 98 \text{ g/equiv} $$
The equivalent weight of phosphoric acid (H₃PO₄) in the given reaction is $98 \text{ g/equiv}$.
More Information
Phosphoric acid has three protons that it can potentially donate, but in this specific reaction, it only donates one, which is why the equivalent weight is calculated using that value.
Tips
Avoid confusing the total number of hydrogen ions in the acid with the number of ions donated in the specific reaction. Always consider the reaction context.
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