What Is The Molar Mass Of KHP?
The correct answer and explanation is :
The molar mass of potassium hydrogen phthalate (KHP) is approximately 204.23 g/mol.
Explanation:
Potassium hydrogen phthalate (KHP) is a commonly used primary standard in acid-base titrations due to its stability and known composition. The formula for KHP is C8H5KO4. To calculate its molar mass, we add the atomic masses of the elements that make up the compound.
The molecular formula of KHP contains:
- Carbon (C): The atomic mass of carbon is 12.01 g/mol. There are 8 carbon atoms in KHP, so the total mass contributed by carbon is: $$
8 \times 12.01 \, \text{g/mol} = 96.08 \, \text{g/mol}
$$ - Hydrogen (H): The atomic mass of hydrogen is 1.008 g/mol. There are 5 hydrogen atoms in KHP, so the total mass contributed by hydrogen is: $$
5 \times 1.008 \, \text{g/mol} = 5.04 \, \text{g/mol}
$$ - Potassium (K): The atomic mass of potassium is 39.10 g/mol. Since there is one potassium atom in KHP, the mass contributed by potassium is: $$
1 \times 39.10 \, \text{g/mol} = 39.10 \, \text{g/mol}
$$ - Oxygen (O): The atomic mass of oxygen is 16.00 g/mol. There are 4 oxygen atoms in KHP, so the total mass contributed by oxygen is: $$
4 \times 16.00 \, \text{g/mol} = 64.00 \, \text{g/mol}
$$
Now, summing the contributions from all the elements:
$$
96.08 \, \text{g/mol} + 5.04 \, \text{g/mol} + 39.10 \, \text{g/mol} + 64.00 \, \text{g/mol} = 204.23 \, \text{g/mol}
$$
Thus, the molar mass of KHP is 204.23 g/mol.
This molar mass is useful for calculating the number of moles of KHP in a given mass, particularly when KHP is used in standardizing solutions like sodium hydroxide (NaOH) in titrations. Since KHP is a solid and relatively stable, it’s a preferred choice for precise acid-base titration, where the molar mass allows for accurate determination of concentrations.