100 ppm to Molarity: Formula and Worked Examples

This calculator converts 100 parts per million (ppm) into molarity when you provide the solute’s molar mass. Enter that mass in grams per mole to get an approximate concentration in mol/L; the conversion assumes a dilute water-like solution with density near 1 kg/L.

Formula

For a dilute aqueous solution, 1 ppm by mass is approximately 1 mg/L. Convert milligrams per liter to grams per liter, then divide by molar mass: M = C / W. Here, M is molarity in mol/L, C is concentration in mg/L (numerically approximately ppm), and W is molar mass in g/mol. The factors of 1,000 mg/g cancel with 1,000 mL/L, giving the compact expression M = ppm ÷ (1,000 × W) if ppm is entered as mg/kg and solution density is treated as 1 kg/L; equivalently, for ppm entered as mg/L, M = ppm ÷ (1,000 × W).

Important correction: the calculator’s expression above is ppm / mw, which gives mmol/L numerically, not mol/L. To report mol/L, the expression must include division by 1,000. Therefore use the corrected result below: 100 ppm of a 58.44 g/mol solute is 0.001711 mol/L. A calculator should express this as ppm / (1000 * mw).

Worked Example

Using the defaults, concentration is 100 ppm and molar mass is 58.44 g/mol. Under the dilute-water approximation, 100 ppm ≈ 100 mg/L = 0.100 g/L. Divide by molar mass: 0.100 g/L ÷ 58.44 g/mol = 0.001711 mol/L, or 1.711 mmol/L. This is the correct molarity; the displayed calculator expression needs the factor of 1,000 noted above.

100 ppm to Molarity: 100 Useful Solute Examples

The list gives approximate molarity for 100 ppm by mass in dilute water, using each compound’s molar mass. It is intended for students and lab users who need quick estimates; check density and chemical form for precise work.

Common inorganic salts

1. Sodium chloride (NaCl): 0.00171 M. Its molar mass is 58.44 g/mol, making it a convenient reference example.
2. Potassium chloride (KCl): 0.00134 M. Use the anhydrous formula mass of 74.55 g/mol.
3. Calcium chloride (CaCl₂): 0.000901 M. Hydrated calcium chloride requires the hydrate’s larger molar mass.
4. Magnesium chloride (MgCl₂): 0.00105 M. The value assumes anhydrous MgCl₂ at 95.21 g/mol.
5. Sodium sulfate (Na₂SO₄): 0.000704 M. This is formula-unit molarity, not sodium-ion molarity.
6. Potassium sulfate (K₂SO₄): 0.000574 M. Dissociation does not change the calculated formula-unit concentration.
7. Sodium bicarbonate (NaHCO₃): 0.00119 M. This common buffer ingredient has a molar mass near 84.01 g/mol.
8. Sodium carbonate (Na₂CO₃): 0.000943 M. Use anhydrous carbonate, not washing-soda decahydrate.
9. Ammonium chloride (NH₄Cl): 0.00187 M. Its 53.49 g/mol molar mass gives a relatively high value.
10. Sodium nitrate (NaNO₃): 0.00118 M. The conversion is based on the full formula mass, 84.99 g/mol.
11. Potassium nitrate (KNO₃): 0.000989 M. This is approximately 0.989 mmol/L.
12. Calcium nitrate (Ca(NO₃)₂): 0.000610 M. The figure assumes anhydrous material, 164.09 g/mol.
13. Magnesium sulfate (MgSO₄): 0.000831 M. Epsom salt is often hydrated, so identify the form before using this number.
14. Copper(II) sulfate (CuSO₄): 0.000626 M. Pentahydrate has a different molarity at the same mass concentration.
15. Iron(II) sulfate (FeSO₄): 0.000658 M. This assumes the anhydrous salt rather than its common heptahydrate.

Acids and bases

16. Hydrochloric acid (HCl): 0.00274 M. Its small molar mass, 36.46 g/mol, yields more moles per gram.
17. Nitric acid (HNO₃): 0.00159 M. The estimate uses a molar mass of 63.01 g/mol.
18. Sulfuric acid (H₂SO₄): 0.00102 M. This is molecular molarity, not acid-equivalent concentration.
19. Phosphoric acid (H₃PO₄): 0.00102 M. Its molar mass is approximately 97.99 g/mol.
20. Acetic acid (CH₃COOH): 0.00167 M. The result refers to pure acetic acid mass in the solution.
21. Formic acid (HCOOH): 0.00217 M. Its 46.03 g/mol molar mass explains the higher value.
22. Sodium hydroxide (NaOH): 0.00250 M. This calculation uses 40.00 g/mol and assumes the stated ppm is NaOH itself.
23. Potassium hydroxide (KOH): 0.00178 M. Carbon dioxide uptake can alter the composition of stored solutions.
24. Calcium hydroxide [Ca(OH)₂]: 0.00135 M. Solubility may limit whether this concentration can exist in water.
25. Ammonia (NH₃): 0.00587 M. The result uses NH₃ molar mass, not the mass of an ammonia-water product.

Simple organic compounds

26. Methanol (CH₃OH): 0.00312 M. Its molar mass is 32.04 g/mol.
27. Ethanol (C₂H₅OH): 0.00217 M. This is the concentration of ethanol, not proof of a beverage strength.
28. 1-Propanol (C₃H₇OH): 0.00166 M. The calculation uses 60.10 g/mol.
29. Acetone (C₃H₆O): 0.00172 M. Its molar mass is 58.08 g/mol.
30. Formaldehyde (CH₂O): 0.00333 M. The result is for formaldehyde mass, independent of its commercial solution label.
31. Urea [CO(NH₂)₂]: 0.00167 M. Its molar mass is 60.06 g/mol.
32. Glucose (C₆H₁₂O₆): 0.000555 M. At this mass concentration, the result is about 0.555 mmol/L.
33. Fructose (C₆H₁₂O₆): 0.000555 M. It shares glucose’s formula and molar mass.
34. Sucrose (C₁₂H₂₂O₁₁): 0.000292 M. Its larger 342.30 g/mol mass means fewer moles per liter.
35. Glycerol (C₃H₈O₃): 0.00109 M. The calculation uses 92.09 g/mol.
36. Ethylene glycol (C₂H₆O₂): 0.00161 M. This is a concentration conversion, not handling guidance.
37. Propylene glycol (C₃H₈O₂): 0.00131 M. Its molar mass is about 76.10 g/mol.
38. Citric acid (C₆H₈O₇): 0.000520 M. Citric acid monohydrate has a different formula mass.
39. Lactic acid (C₃H₆O₃): 0.00111 M. The estimate uses 90.08 g/mol.
40. Oxalic acid (H₂C₂O₄): 0.00111 M. Dihydrate crystals require using the hydrated molar mass.

Organic solvents and aromatics

41. Benzene (C₆H₆): 0.00128 M. Its molar mass is 78.11 g/mol.
42. Toluene (C₇H₈): 0.00109 M. The value is a mathematical conversion, not a safety threshold.
43. Ethylbenzene (C₈H₁₀): 0.000943 M. Use its 106.17 g/mol formula mass.
44. Styrene (C₈H₈): 0.000961 M. This assumes the concentration is expressed as styrene mass.
45. Phenol (C₆H₆O): 0.00106 M. The 94.11 g/mol molar mass sets the conversion.
46. Aniline (C₆H₇N): 0.00107 M. This uses a molar mass of 93.13 g/mol.
47. Naphthalene (C₁₀H₈): 0.000781 M. Its low water solubility may make 100 mg/L unsuitable in water.
48. Chloroform (CHCl₃): 0.000839 M. The number uses 119.38 g/mol.
49. Dichloromethane (CH₂Cl₂): 0.00118 M. Its molar mass is approximately 84.93 g/mol.
50. Carbon tetrachloride (CCl₄): 0.000651 M. This is based on a formula mass of 153.82 g/mol.
51. Diethyl ether (C₄H₁₀O): 0.00135 M. The assumed molar mass is 74.12 g/mol.
52. Acetonitrile (C₂H₃N): 0.00244 M. Its small molar mass is about 41.05 g/mol.
53. Dimethyl sulfoxide (C₂H₆OS): 0.00128 M. The conversion uses 78.13 g/mol.
54. Dimethylformamide (C₃H₇NO): 0.00137 M. Its molar mass is 73.09 g/mol.
55. 1,4-Dioxane (C₄H₈O₂): 0.00114 M. The calculation assumes 88.11 g/mol.

Common gases and dissolved molecules

56. Carbon dioxide (CO₂): 0.00227 M. This treats ppm as mass concentration, not gas-phase volume ppm.
57. Carbon monoxide (CO): 0.00357 M. The 28.01 g/mol mass gives 3.57 mmol/L.
58. Sulfur dioxide (SO₂): 0.00156 M. Dissolved reactions can make total sulfur species differ from free SO₂.
59. Hydrogen sulfide (H₂S): 0.00293 M. The conversion is not a gas-volume mixing-ratio conversion.
60. Oxygen (O₂): 0.00312 M. This uses 32.00 g/mol and assumes 100 mg/L dissolved mass.
61. Nitrogen (N₂): 0.00357 M. The result applies only when ppm denotes mass per mass.
62. Hydrogen peroxide (H₂O₂): 0.00294 M. Its molar mass is 34.01 g/mol.
63. Ozone (O₃): 0.00208 M. The calculation uses 48.00 g/mol.
64. Chlorine (Cl₂): 0.00141 M. This is molecular chlorine mass, not a chlorine-equivalent reporting convention.
65. Fluorine (F₂): 0.00263 M. The figure uses 38.00 g/mol.
66. Nitrous oxide (N₂O): 0.00227 M. Its formula mass is approximately 44.01 g/mol.
67. Methane (CH₄): 0.00623 M. This is a mass-based aqueous estimate, not ppm by volume in air.

Metals and elements

68. Iron (Fe): 0.00179 M. The value uses elemental iron’s atomic mass, 55.845 g/mol.
69. Copper (Cu): 0.00157 M. This is total copper molarity if ppm is reported as elemental Cu.
70. Zinc (Zn): 0.00153 M. Use this when the measured mass is zinc, not a zinc salt.
71. Lead (Pb): 0.000483 M. The conversion is arithmetic and does not describe a safe exposure level.
72. Mercury (Hg): 0.000499 M. The result treats the reported mass as elemental mercury.
73. Silver (Ag): 0.000927 M. The atomic mass used is 107.87 g/mol.
74. Gold (Au): 0.000508 M. This uses elemental gold’s 196.97 g/mol mass.
75. Aluminum (Al): 0.00371 M. The atomic mass is 26.98 g/mol.
76. Manganese (Mn): 0.00182 M. This value is for elemental manganese concentration.
77. Nickel (Ni): 0.00170 M. The calculation uses 58.69 g/mol.
78. Chromium (Cr): 0.00192 M. Chromium oxidation state does not change elemental-mass conversion, but it changes chemical identity.
79. Arsenic (As): 0.00133 M. This is elemental arsenic molarity, not arsenate formula-unit molarity.
80. Selenium (Se): 0.00127 M. The atomic mass used is 78.97 g/mol.
81. Boron (B): 0.00925 M. Its low atomic mass gives a comparatively large molar amount.

Additional laboratory compounds

82. Sodium fluoride (NaF): 0.00238 M. Its formula mass is 41.99 g/mol.
83. Potassium iodide (KI): 0.000602 M. This uses 166.00 g/mol.
84. Sodium hypochlorite (NaClO): 0.00134 M. Commercial solutions may be labeled by available chlorine instead.
85. Calcium carbonate (CaCO₃): 0.000999 M. Its limited solubility can prevent a true 100 mg/L dissolved solution.
86. Sodium thiosulfate (Na₂S₂O₃): 0.000632 M. Hydrated crystals need the hydrate’s molar mass instead.
87. Potassium permanganate (KMnO₄): 0.000633 M. The conversion uses a molar mass of 158.03 g/mol.
88. Sodium phosphate (Na₃PO₄): 0.000610 M. This assumes anhydrous trisodium phosphate.
89. Ammonium sulfate [(NH₄)₂SO₄]: 0.000757 M. The result is formula-unit molarity.
90. Silver nitrate (AgNO₃): 0.000589 M. Its molar mass is 169.87 g/mol.
91. Barium chloride (BaCl₂): 0.000480 M. This assumes anhydrous barium chloride, not the dihydrate.
92. Aluminum sulfate [Al₂(SO₄)₃]: 0.000292 M. Hydrated aluminum sulfate has a substantially different mass per mole.
93. Sodium acetate (CH₃COONa): 0.00122 M. The number assumes anhydrous sodium acetate.
94. Potassium acetate (CH₃COOK): 0.00102 M. Its formula mass is about 98.14 g/mol.
95. Acetaldehyde (C₂H₄O): 0.00227 M. The calculation uses 44.05 g/mol.
96. Benzoic acid (C₇H₆O₂): 0.000819 M. Its low solubility can matter when interpreting an aqueous concentration.
97. Salicylic acid (C₇H₆O₃): 0.000724 M. The value follows from its 138.12 g/mol molar mass.
98. Caffeine (C₈H₁₀N₄O₂): 0.000515 M. This uses 194.19 g/mol.
99. Aspirin (C₉H₈O₄): 0.000555 M. The result uses acetylsalicylic acid’s 180.16 g/mol mass.
100. Glycine (C₂H₅NO₂): 0.00133 M. Its molar mass is about 75.07 g/mol.

How to Use This List

Find the exact chemical and formula form, then use its molar mass in grams per mole. For a different ppm value, scale the listed molarity in direct proportion: 250 ppm gives 2.5 times the 100 ppm value. Confirm whether the source means mass-based ppm, mg/L, elemental content, or gas-volume ppm; these are not interchangeable. For accurate work outside dilute water, use solution density and the precise definition of ppm.

Frequently Asked Questions

What does 100 ppm mean?
By mass, it means 100 parts solute per million parts solution, equivalent to 100 mg/kg.

Is 100 ppm always 100 mg/L?
No. That approximation assumes a solution density near 1 kg/L, as for dilute water solutions.

How do I convert ppm to molarity?
For dilute water, divide ppm (treated as mg/L) by 1,000 times the molar mass in g/mol.

Why does molar mass matter?
The same solute mass contains fewer moles when its molecules or formula units are heavier.

Can I use this for hydrates?
Yes, but use the hydrate’s full formula mass and confirm whether ppm refers to the hydrate or anhydrous compound.

Does ppm by volume use this list?
No. Gas-volume ppm is a mole-fraction measure and needs different conversion data, such as pressure and temperature to obtain concentration.

Final Thoughts

For 100 ppm by mass in dilute water, molarity depends on the specific solute’s molar mass. Treat the list as an estimate, verify chemical form and ppm convention, and include the factor of 1,000 when converting mg/L to mol/L.

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in ppm | Concentration | ppm | 100 | 0
in mw | Molar mass | g/mol | 58.44 | 0
out molarity | Molarity | mol/L | ppm / mw | 6