Molar mass of potassium hydrogen phthalate (C₈H₅KO₄)

The molar mass of potassium hydrogen phthalate (C₈H₅KO₄) is 204.2223 g/mol, summed from the IUPAC standard atomic weights of C x 8, H x 5, K, O x 4. The primary standard used to standardise alkali solutions.

Mass of sample

Amount of substance

mol

Molar mass

204.2223g/mol

= Exact Molar mass of potassium hydrogen phthalate

Moles in the sample mass: 0.048 966 249 mol
Mass of that amount of substance: 204.2223
Molecules in the sample mass: 2.94882e+22

Show the working

Mass of sample = 10
Amount of substance = 1
Molar mass = 12.011*8 + 1.008*5 + 39.0983 + 15.999*4 = 204.222
Moles in the sample mass = 10 / 204.222 = 0.048 966 2
Mass of that amount of substance = 1 * 204.222 = 204.222
Molecules in the sample mass = 0.048 966 2 * NA = 2.94882e+22

Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.

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The formula

Molar mass = sum over elements of (atomic weight x number of atoms)
For C₈H₅KO₄: 12.011 x 8 + 1.008 x 5 + 39.0983 + 15.999 x 4 = 204.2223 g/mol
Moles = mass / molar mass; mass = moles x molar mass
Molecules = moles x 6.02214076 x 10^23 (the Avogadro constant, exact by definition)

Molar mass in grams per mole is numerically equal to the molecular mass in daltons, so this figure doubles as the molecular weight.

Atomic weights are the IUPAC 2021 standard values. Several elements have a range rather than a single value because isotope ratios vary between sources; the conventional single value is used here.

The primary standard used to standardise alkali solutions.

Composition by mass

Element	Atoms	Atomic weight	Contribution (g/mol)	Share of mass
Carbon (C)	8	12.011	96.088	47.051 %
Oxygen (O)	4	15.999	63.996	31.336 %
Potassium (K)	1	39.0983	39.0983	19.145 %
Hydrogen (H)	5	1.008	5.04	2.4679 %

Contributions add to the molar mass of 204.2223 g/mol. Atomic weights are the IUPAC 2021 standard values.

Frequently asked

What is the molar mass of potassium hydrogen phthalate?

204.2223 g/mol, for the formula C₈H₅KO₄.

How do you convert grams of potassium hydrogen phthalate to moles?

Divide the mass in grams by 204.2223 g/mol. One gram of potassium hydrogen phthalate is 0.00489662 mol.

How many grams are in one mole of potassium hydrogen phthalate?

204.2223 g, by definition of the molar mass.

Is molar mass the same as molecular weight?

Numerically yes, for the purposes of this calculation. Molecular weight is a dimensionless ratio and molar mass carries units of g/mol, but the digits are identical.

Where the numbers come from

IUPAC 2021 standard atomic weights; Avogadro constant fixed by the 2019 SI.