Understanding Norwegian Saltpeter

The question asks to identify the compound commonly known as ‘Norwegian saltpeter’. This is a common name given to a specific chemical compound, usually associated with its historical production methods or geographical origin.

What is Saltpeter?

The term ‘saltpeter’ (or saltpetre) generally refers to potassium nitrate ($\text{KNO}_3$). However, historically, the term or similar variations were also used for other nitrate compounds, especially those used as fertilizers or in gunpowder. Different types of "saltpeter" were named based on their source or composition.

Identifying Norwegian Saltpeter

Norwegian saltpeter is a name specifically given to calcium nitrate, which has the chemical formula $\text{Ca(NO}_3\text{)}_2$. This name originated because calcium nitrate was one of the first synthetic nitrogen fertilizers produced on a large scale in Norway, primarily by the Norsk Hydro company in the early 20th century. They used the Birkeland–Eyde process to fix atmospheric nitrogen, reacting nitric acid (produced from nitrogen) with lime or calcium carbonate to produce calcium nitrate.

Analyzing the Options

Let's look at the given options:

1. Nitrous oxide: This compound ($\text{N}_2\text{O}$) is commonly known as ‘laughing gas’. It is not a nitrate salt used as fertilizer in the way saltpeter is.
2. Calcium nitrate: This compound ($\text{Ca(NO}_3\text{)}_2$) is calcium salt of nitric acid. As discussed, it is historically known as Norwegian saltpeter due to its production in Norway. It is a widely used fertilizer, particularly for acidic soils.
3. Sodium nitrate: This compound ($\text{NaNO}_3$) is commonly known as ‘Chilean saltpeter’ because large deposits of it were historically found and mined in the Atacama Desert of Chile.
4. Potassium nitrate: This compound ($\text{KNO}_3$) is the original ‘saltpeter’ or ‘nitre’. It is used in fertilizers, gunpowder, and food preservation. While it is a type of saltpeter, it is not specifically called Norwegian saltpeter.

Based on the historical naming conventions and the chemical properties, calcium nitrate ($\text{Ca(NO}_3\text{)}_2$) is the compound known as Norwegian saltpeter.

Comparison of Saltpeter Types

Conclusion on Norwegian Saltpeter

The compound referred to as ‘Norwegian saltpeter’ is calcium nitrate, distinguished by its historical large-scale production in Norway. Other nitrate salts have different common names reflecting their origins or properties.

Revision Table: Key Compounds and Names

Reviewing the different names helps solidify understanding:

• Norwegian Saltpeter: Calcium Nitrate ($\text{Ca(NO}_3\text{)}_2$)
• Chilean Saltpeter: Sodium Nitrate ($\text{NaNO}_3$)
• Saltpeter/Nitre: Potassium Nitrate ($\text{KNO}_3$)
• Laughing Gas: Nitrous Oxide ($\text{N}_2\text{O}$)

Additional Information on Calcium Nitrate

Calcium nitrate is an important fertilizer because it provides both nitrogen (essential for plant growth) and calcium (important for cell walls and other plant functions). It is highly soluble in water, making its nitrogen readily available to plants. It is particularly beneficial in preventing or treating calcium deficiencies in plants and can help improve soil structure in some cases.