Molar Mass of Ammonia (NH₃)
Learn how chemists calculate the molar mass of Ammonia (NH₃), with a clear formula breakdown, worked steps, and study notes.
Quick answer
The molar mass of Ammonia (NH₃) is
17.031g/mol
One mole of Ammonia therefore has a mass of 17.031 grams—the value you use for stoichiometry and laboratory preparation.
Reviewed for educational accuracy · Accuracy policy
- CAS Registry Number
- 7664-41-7
- PubChem CID
- 222
- SMILES
- N
Step-by-step calculation
Let's find the molar mass of Ammonia (NH₃) together—step by step, as if you are seeing the formula for the first time.
Step 1 — Look at the chemical formula
The formula is NH₃. Each letter stands for an element. The little number after a letter (the subscript) tells you how many atoms of that element are in one molecule or formula unit.
- 1 Nitrogen atom (N)
- 3 Hydrogen atoms (H)
Step 2 — Look up each atomic mass
Atomic mass comes from the periodic table. It is the average mass of one mole of atoms of that element, in grams per mole (g/mol). Think of it as the "price tag" for one mole of that element.
- Nitrogen (N) = 14.007 g/mol
- Hydrogen (H) = 1.008 g/mol
Step 3 — Multiply atoms × atomic mass
Why multiply? If one oxygen atom "costs" about 16 g/mol, then two oxygen atoms cost twice as much. Each element's contribution is: number of atoms × atomic mass.
- 1 × 14.007 = 14.007 g/mol (Nitrogen)
- 3 × 1.008 = 3.024 g/mol (Hydrogen)
Step 4 — Add the contributions
Why add? The molar mass of the whole compound is simply the total mass of every atom in the formula. Add each element's contribution:
14.007 + 3.024 = 17.031 g/mol
Step 5 — Final answer
Molar mass of Ammonia = 17.031 g/mol
That means one mole of Ammonia (NH₃) has a mass of about 17.03 grams.
Quick summary
Read the formula → count atoms → look up atomic masses → multiply → add → report g/mol. For NH₃, the total is 17.031 g/mol.
Common beginner mistakes
- Calling NH₃ a strong base — it is weak (Kb = 1.8 × 10⁻⁵).
- Confusing NH₃ (17.03) with NH₄⁺ (18.04) molar mass in stoichiometry.
- Writing NH₄OH as a stable molecular species — it is better described as NH₃(aq) + H₂O equilibrium.
Memory trick
Link 17 g/mol to being roughly half of air's average molar mass.
Mini practice
Without looking above, list the atoms in NH₃ and write one multiplication line for the heaviest element. Then check your work against Step 3.
Real-world example
If a recipe asks for 0.100 mol of Ammonia, mass needed = 0.100 × 17.031 = 1.703 g. That is how chemists turn a mole amount into a weighable sample.
Atomic contribution table
Each row shows how much mass one element contributes to the total for NH₃.
| Element | Atoms | Atomic mass | Contribution | Mass % |
|---|---|---|---|---|
| N | 1 | 14.007 | 14.007 g/mol | 82.2% |
| H | 3 | 1.008 | 3.024 g/mol | 17.8% |
| Total molar mass | 17.031 g/mol | 100% | ||
Mass contribution chart
Count every atom in this formula, multiply by atomic mass, then add. That total is the molar mass used in lab weighing.
Download study sheets
Save a printable summary, revision sheet, practice worksheet, or laboratory reference for Ammonia (NH₃).
Practice this calculation
Without looking above, write the atom count for NH₃, then compute the molar mass. Check your answer against 17.031 g/mol.
Next challenge: how many grams are in 0.250 mol of Ammonia? Multiply 0.250 × 17.031 to get 4.258 g.
Physical and chemical properties
Physical properties
| Appearance | Colorless gas or liquefied clear liquid (under pressure) |
| Color | Colorless |
| Odor | Pungent, characteristic (sharp, irritating) |
| State (STP) | Gas |
| Density | 0.771 g/L at STP (gas); 0.682 g/mL (liquid at −33 °C) |
| Melting point | −77.73 °C |
| Boiling point | −33.34 °C |
| Solubility | 540 g/L water at 20 °C (highly soluble — 'ammonium hydroxide') |
| Crystal structure | Cubic (solid NH₃, hydrogen-bonded) |
Chemical properties
| Classification | Weak base / pnictogen hydride |
| Family | Group 15 hydride (nitrogen trihydride) |
| Basicity | Weak base (Kb = 1.8 × 10⁻⁵, pKb = 4.75) |
| Polarity | Polar (dipole moment 1.47 D) |
| Geometry | Trigonal pyramidal |
| Bond angle | 107.8° |
| Oxidation states | N: −3, H: +1 |
Applications
Industrial uses
- Nitrogen fertilizer production (Haber–Bosch → urea, ammonium salts)
- Refrigerant R-717 in industrial cold storage
- Nylon precursor (adipic acid via nitric acid from NH₃ oxidation)
- Scrubbing acid gases in power plants (forms ammonium sulfate)
Laboratory uses
- Qualitative analysis complex ion formation (Cu²⁺, Ag⁺)
- Source of NH₄⁺ for buffer solutions
- Organic synthesis (amidation, reductive amination)
Agricultural runoff of ammonium fertilizers causes eutrophication; atmospheric NH₃ contributes to PM₂.₅ aerosol formation.
Microbial nitrogen fixation converts N₂ to NH₃ biologically; urea cycle converts toxic NH₃ to urea in mammals for excretion.
Preparation and production
Haber–Bosch: N₂ + 3 H₂ ⇌ 2 NH₃. Laboratory: warm ammonium chloride with NaOH: NH₄Cl + NaOH → NH₃ + NaCl + H₂O.
Global ammonia production exceeds 180 million tonnes annually, primarily from natural gas-derived hydrogen. Green ammonia projects use renewable electrolytic hydrogen.
Important reactions of Ammonia
N₂(g) + 3 H₂(g) ⇌ 2 NH₃(g)
- Reaction type
- Haber–Bosch synthesis
- Conditions
- 400–500 °C, 150–300 atm, Fe catalyst with K₂O/Al₂O₃ promoters
- Explanation
- Exothermic equilibrium (ΔH = −92 kJ/mol); high pressure favors products; catalyst allows reasonable rate at moderate temperature.
- Products
- Ammonia
- Why it matters
- Global fertilizer and chemical industry foundation
Related ideas: Equilibrium · Catalysis · Industrial chemistry
NH₃(aq) + HCl(aq) → NH₄Cl(aq)
- Reaction type
- Acid–base neutralization
- Conditions
- Aqueous, room temperature
- Explanation
- Ammonia accepts proton from strong acid forming ammonium chloride — white smoke when HCl and NH₃ vapors meet.
- Products
- Ammonium chloride
- Why it matters
- Demonstration of gas-phase acid–base reaction, smoke screens
Related ideas: Brønsted acids/bases · Salt formation
4 NH₃(g) + 5 O₂(g) → 4 NO(g) + 6 H₂O(g)
- Reaction type
- Catalytic oxidation (Ostwald step 1)
- Conditions
- Pt-Rh gauze, 800–900 °C
- Explanation
- Partial oxidation of ammonia to nitric oxide, first step in nitric acid manufacture.
- Products
- Nitric oxide and water
- Why it matters
- Nitric acid and explosives precursor production
Related ideas: Redox · Catalysis · Industrial oxidation
Cu²⁺(aq) + 4 NH₃(aq) → [Cu(NH₃)₄]²⁺(aq)
- Reaction type
- Complex ion formation
- Conditions
- Excess ammonia, aqueous
- Explanation
- Ammonia acts as Lewis base, displacing water from copper(II) aqua complex to form deep blue tetraamminecopper(II).
- Products
- Tetraamminecopper(II) ion
- Why it matters
- Qualitative analysis for Cu²⁺, understanding coordination chemistry
Related ideas: Coordination compounds · Lewis bases · Complex ions
History and discovery
Priestley prepared ammonia from sal ammoniac (1774). Haber patented synthetic ammonia synthesis (1908); Bosch scaled it industrially (1913), earning Nobel Prizes for both. The process transformed agriculture and warfare (explosives from nitric acid).
Joseph Priestley, 1774 — collected ammonia gas from heating ammonium chloride with lime.
Interesting facts
- NH₃ molar mass 17.03 g/mol is lighter than air (avg ~29 g/mol) — ammonia gas rises.
- Household 'ammonia' is ~5–10% NH₃ in water, not anhydrous gas.
- Fish excrete NH₃ directly; mammals convert it to less toxic urea.
- Liquid NH₃ dissolves alkali metals to form conductive blue solutions (solvated electrons).
Comparison with similar compounds
NH₃ (17.03 g/mol) is a weak base and gas at STP; NaOH (40.00 g/mol) is a strong base and solid — both are nitrogen-containing but chemically distinct.
Storage, handling, and safety
Store anhydrous NH₃ in pressure vessels designed for its vapor pressure (~8.6 atm at 20 °C). Aqueous ammonia (ammonium hydroxide) in vented containers away from acids and oxidizers.
Highly irritating and toxic by inhalation. Use respiratory protection in enclosed spaces. Anhydrous ammonia causes severe frostbite on contact (auto-refrigeration upon release). Work downwind and with emergency water showers accessible.
Toxic by inhalation; corrosive to respiratory tract. Anhydrous form causes cold burns. Flammable in narrow concentration range (15–28% in air).
- Asphyxiation and pulmonary edema at high concentrations
- Frostbite from liquefied gas contact
- Explosive mixtures with air in confined spaces
- Violent reaction with strong oxidizers and halogens
Classification: GHS: Acute Tox. 3 (inhalation), Skin Corr. 1B
Exam notes and student tips
Exam notes
- Molar mass NH₃ = 14.01 + 3(1.008) = 17.03 g/mol.
- Haber process: N₂ + 3 H₂ ⇌ 2 NH₃ (high P, moderate T, Fe catalyst).
- Weak base: pKb = 4.75; 0.1 M NH₃ has pH ≈ 11.1.
- Complex ion: Cu²⁺ + 4 NH₃ → [Cu(NH₃)₄]²⁺ (deep blue, used in qualitative analysis).
Student tips
- Link 17 g/mol to being roughly half of air's average molar mass.
- Draw trigonal pyramid and lone pair for Lewis base questions.
- For fertilizer stoichiometry, trace Haber → HNO₃ or urea pathways.
Common mistakes
- Calling NH₃ a strong base — it is weak (Kb = 1.8 × 10⁻⁵).
- Confusing NH₃ (17.03) with NH₄⁺ (18.04) molar mass in stoichiometry.
- Writing NH₄OH as a stable molecular species — it is better described as NH₃(aq) + H₂O equilibrium.
Misconceptions
- Smelling ammonia is dangerous at high concentrations — the odor warns at low levels but anhydrous releases can overwhelm quickly.
- Ammonium (NH₄⁺) is not a base — it is a weak acid (conjugate of NH₃).
- All nitrogen in fertilizer is immediately plant-available — conversion to nitrate by soil bacteria takes time.
Practice questions
1. Calculate the molar mass of NH₃.
Show answer
14.01 + 3(1.008) = 17.03 g/mol
2. How many moles of H₂ needed to produce 34 g of NH₃ via Haber process?
Hint: N₂ + 3 H₂ → 2 NH₃ — 3 mol H₂ per 2 mol NH₃.
Show answer
34 g ÷ 17.03 g/mol = 2.0 mol NH₃; needs 3 × 2.0 = 6.0 mol H₂
3. Why is high pressure used in the Haber process?
Show answer
The reaction N₂ + 3 H₂ ⇌ 2 NH₃ decreases gas moles (4 → 2); high pressure shifts equilibrium toward NH₃ per Le Chatelier.
4. Is ammonia a strong or weak base?
Show answer
Weak base — Kb = 1.8 × 10⁻⁵; partial protonation in water.
Frequently asked questions about Ammonia
17.03 g/mol.
Chemistry of Ammonia
The sections above give the number you need for calculations. Here we look more closely at how Ammonia (NH₃) behaves chemically—so the molar mass connects to real reactions, properties, and laboratory practice.
Ammonia (NH₃) is a colorless gas with molar mass 17.03 g/mol (N 14.01 + 3 × 1.008), characterized by a pungent odor detectable below 1 ppm. Its trigonal pyramidal geometry (107° bond angle) and lone pair on nitrogen make it a Brønsted base — it accepts protons to form ammonium ion NH₄⁺ — and a Lewis base that forms coordination complexes with transition metals.
The Haber–Bosch process converts N₂ and H₂ to NH₃ at 400–500 °C and 150–300 atm over iron catalyst, consuming roughly 1–2% of global energy production. Fixed nitrogen from ammonia synthesis supports half the world's food supply through fertilizer (urea, ammonium nitrate, ammonium phosphate). NH₃ also serves as a hydrogen carrier in emerging clean-energy schemes because it liquefies at manageable pressure (~10 bar at room temperature) unlike H₂.
NH₃ contains nitrogen with three N–H single bonds and one lone pair. The molecular formula shows 1:3 N:H ratio. In aqueous solution, a small fraction protonates: NH₃ + H₂O ⇌ NH₄⁺ + OH⁻ (Kb = 1.8 × 10⁻⁵), making ammonia a weak base.
NH₃ is a weak base and reducing agent. It burns in oxygen with a yellow-green flame: 4 NH₃ + 3 O₂ → 2 N₂ + 6 H₂O. With excess O₂ and Pt catalyst it oxidizes to NO (Ostwald process first step). It forms ammines with Cu²⁺ (deep blue [Cu(NH₃)₄]²⁺), Ag⁺ (Tollens' reagent), and other metal ions. Liquid ammonia is a protic solvent analogous to water but with lower dielectric constant.
The Haber–Bosch Process and Modern Agriculture
Fritz Haber and Carl Bosch's industrial synthesis of ammonia from atmospheric N₂ and H₂ (N₂ + 3 H₂ ⇌ 2 NH₃, Fe catalyst, high pressure/temperature) is often cited as one of the most consequential inventions in history: it broke the natural limit on fixed nitrogen available for fertilizer, enabling the population growth of the 20th and 21st centuries, but at the cost of consuming roughly 1–2% of global energy production and a large share of anthropogenic reactive nitrogen entering ecosystems.
Ammonia as a Weak Base vs. Strong Bases
Unlike NaOH or KOH, which are already ionic hydroxides that dissolve to release OH⁻ directly, NH₃ must react with water (NH₃ + H₂O ⇌ NH₄⁺ + OH⁻, Kb = 1.8 × 10⁻⁵) to generate a comparatively small hydroxide concentration, making ammonia solutions far less caustic per mole than strong alkali solutions — an important distinction for handling household ammonia cleaners safely.
Ammonia vs. the Ammonium Ion (NH₄⁺)
Ammonia (NH₃, a neutral molecule and Brønsted base) and ammonium (NH₄⁺, its protonated conjugate acid) are frequently confused but behave very differently: NH₃ is volatile and basic, while NH₄⁺ salts are generally non-volatile, water-soluble, and mildly acidic in solution — a distinction critical to understanding fertilizer chemistry, soil nitrogen cycling, and acid-base equilibria.
Household Cleaning Chemistry and Hazards
Dilute aqueous ammonia is a common household glass and surface cleaner because it cuts through grease and leaves a streak-free finish without the corrosivity of stronger alkalis, but mixing ammonia-based cleaners with chlorine bleach is dangerous: it generates toxic chloramine gases, a well-documented cause of household chemical poisoning incidents.
The Nitrogen Cycle and Fertilizer Nitrogen
Synthetic ammonia is converted into urea, ammonium nitrate, and ammonium phosphate fertilizers that feed roughly half the world's population by mass-balance estimates, but excess nitrogen not taken up by crops leaches as nitrate or volatilizes, contributing to eutrophication of waterways and nitrous oxide greenhouse gas emissions from soil microbial processes.
Recalculate any formula with the molar mass calculator, compare atoms on the periodic table, or browse more compounds in the base library.
References and further reading
- FAO: Global nitrogen fertilizer statistics
- NIST Chemistry WebBook: NH₃ thermophysical data
- PubChem CID 222: Ammonia compound data