The molecular formula for potassium hydrogen phthalate (abbreviated KHP) is C8H5O4K. What is the molar mass of KHP? Show all work with no rounding errors and have the final answer accurate to at least two decimal places.
The Correct Answer and Explanation is:
Correct Answer:
The molecular formula for potassium hydrogen phthalate (KHP) is C₈H₅O₄K. To calculate the molar mass, we sum the atomic masses of each element in the formula:
- Carbon (C): 12.01 g/mol × 8 = 96.08 g/mol
- Hydrogen (H): 1.008 g/mol × 5 = 5.04 g/mol
- Oxygen (O): 16.00 g/mol × 4 = 64.00 g/mol
- Potassium (K): 39.10 g/mol × 1 = 39.10 g/mol
Total molar mass = 96.08 + 5.04 + 64.00 + 39.10 = 204.22 g/mol
So, the molar mass of C₈H₅O₄K (KHP) is 204.22 g/mol.
Explanation (300 words):
Potassium hydrogen phthalate, commonly known as KHP, is a compound frequently used in chemistry as a primary standard for acid-base titrations. Its molecular formula is C₈H₅O₄K, which tells us the exact number of each type of atom in one molecule of the substance. To find the molar mass of KHP, we need to multiply the number of each atom by its atomic mass and add the results.
There are 8 carbon atoms in KHP. Since each carbon atom has a mass of 12.01 grams per mole, the total contribution from carbon is 96.08 grams per mole. There are 5 hydrogen atoms, and each has a mass of 1.008 grams per mole. This gives 5.04 grams per mole from hydrogen. The molecule also contains 4 oxygen atoms, each with a mass of 16.00 grams per mole, contributing a total of 64.00 grams per mole. Lastly, KHP contains 1 potassium atom, with an atomic mass of 39.10 grams per mole.
Adding all these values together gives the total molar mass of KHP. The molar mass is important because it allows chemists to convert between grams and moles, which is essential when working with chemical reactions and stoichiometry. By knowing the molar mass of KHP to two decimal places, chemists ensure precise measurements and accurate calculations in laboratory settings. This precision is critical when KHP is used to determine the concentration of unknown acids during titrations.
