When nitric acid reacts with ammonia, it produces a white crystalline salt called ammonium nitrate (NH4NO3). As a solid, ammonium nitrate is hygroscopic, which means it attracts moisture. Although the substance dissolves easily in water, it does not form hydrates.
Continue reading to learn more about the surprising reaction between nitric acid and ammonia, as well as the potential hazards.
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What is nitric acid?
Nitric acid is an inorganic substance with the chemical formula HNO3. It’s classified as a strong acid because it completely dissociates into ions when dissolved in water. In its purest form, nitric acid is colourless and highly corrosive. However, when exposed to light or high heat of around 140°C, it decomposes into water, nitrogen oxide, and oxygen and turns yellow.
Nitric acid is commercially produced through the reaction between nitrogen dioxide and water. It’s not a complete reaction as some water and nitrogen dioxide are left. The unconsumed nitrogen dioxide is then further processed to produce more nitric acid.
Commercial-grade nitric acid is produced via the Ostwald process. This process involves the oxidation of anhydrous ammonia using a platinum or rhodium gauze catalyst. The anhydrous ammonia is heated to 227 °C and subjected to nine times the standard atmosphere, or 910 kPa.
What is ammonia?
Ammonia (chemical formula NH3) is an inorganic compound. It exists in a gaseous state at room temperature and is classified as a weak base when in an aqueous solution form. 
Ammonia is formed naturally as a byproduct of organic processes, primarily through the anaerobic decomposition of organisms’ proteins. It’s also produced through the nitrogen fixing process by rhizobia bacteria, which are found in the roots of leguminous plants.
It has many industrial uses and applications. For example, ammonia is an ingredient in some cleaning agents and is crucial to industrial fertiliser production. The chemical is commercially mass-produced through the Haber process, during which nitrogen and hydrogen gases are subjected to high temperatures and pressures in the presence of an iron catalyst.
What happens when acid & ammonia react?
As an alkaline or basic substance, ammonia undergoes a neutralisation reaction when it mixes with an acid. This reaction produces a salt that generally has a neutral pH, although it can also be slightly acidic if a strong acid is used. The exact byproducts that are formed depend on the type of acidic compound that’s used. 
When ammonia reacts with hydrochloric acid, for example, ammonium chloride salt is formed (NH4Cl). The ammonia simply combines with the acid by gaining extra hydrogen plus the cation of the acid. Since ammonia does not contain a hydroxide group, no water is produced during the reaction.
What is the equation for nitric acid & ammonia?
Ammonia is a gas at room temperature, while nitric acid takes the form of an aqueous solution. The neutralisation reaction between the two is a one-way reaction, as shown in the balanced equation below. Just like many other acid-base reactions, it is exothermic. The reverse reaction will require energy input to occur.
What type of reaction does nitric acid & ammonia produce?
The reaction between nitric acid and ammonia is classed as a neutralisation reaction. Neutralisation is when an acid and a base react to form salt and water, which typically have a neutral pH (although not always). In this case, because nitric acid is a strong acid and ammonia is a weak base, the ammonium nitrate salt byproduct can be slightly acidic when dissolved in water.
When dissolved in water, the ions of the ammonium nitrate separate into positively charged and negatively charged ions. The ammonium ion is positively charged while the nitrate ion is negatively charged.
Is the reaction between nitric acid & ammonia dangerous?
Both ammonia and nitric acid are dangerous chemicals in their own right. Ammonia is toxic when inhaled and nitric acid is highly corrosive.
Although the reaction between them is exothermic, it’s not scaldingly hot. Nonetheless, the reaction can cause some nitric acid splashes, which could damage your skin if you’re not wearing the appropriate PPE.
What are the potential hazards for a nitric acid & ammonia reaction?
As well as producing acidic splashes, the reaction between ammonia and nitric acid can also release gaseous ammonia. Both of these are important hazards to be aware of as they can pose a serious risk to your health.
Nitric acid splashes, for example, may burn your skin and mucous membranes, while inhaling ammonia gas can damage your lungs and respiratory tract.
Suffocation
As we’ve already explained, the exothermic reaction between ammonia and nitric acid can sometimes release ammonia gas and nitric acid fumes. Inhaling these fumes is very dangerous and can potentially lead to respiratory problems and even suffocation. 
Abdominal issues & sickness
The byproduct of the reaction itself – ammonium nitrate – is also toxic. If ingested, it can cause a range of abdominal issues and illnesses such as gastritis, acidosis, isosmotic diuresis, and nitrite toxicity.
You can learn more about how to prevent injuries in chemistry here.
Summary
Ammonia is a weak base while nitric acid is a strong acid. When the two react, they undergo an exothermic neutralisation reaction that produces a salt called ammonium nitrate. Unlike some other acid-base reactions that form a neutral salt, ammonium nitrate is acidic because it’s a product of a strong acid and a weak base.
The reaction between nitric acid and ammonia can be hazardous if you don’t take the proper precautions. Some of the potential risks include chemical burns, breathing problems and abdominal issues.
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