What are salts?

<bibimport />

Autoren: Hans-Jürgen Schwarz, NN
back to Fundamentals

Abstract

Salts are compounds made up of cations (e.g., K⁺, Ca²⁺, NH₄⁺) and an anion, such as chloride (Cl^-), nitrate (NO₃^-, that are held together by ionic bonds. They are crystalline materials.

The formation of salts

Salts normally consist of positively charged ions, cations, and negatively charged ions, anions, that form a crystal lattice. In addition, some salts may include the water molecule (H₂O) in the lattice. there are referred to as hydrated salts.

Fig. 1:The crystal lattice of NaCl

Salts are often the result of a neutralisation reaction, i.e., the mixture of an acid with a base.

Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle Na^+ + OH^- + H_3O^+ + Cl^- \rightarrow NaCl + 2H_2O}

base    +     acid       →       salt   +   water

While some salts, such as NaCl are neutral, that is, their solution does not change the normal pH 7 of water, other salts may be alkaline or acidic, depending on the strength of the participating acids and bases:

1. strong acid + strong base → neutral salt + H₂O

2. strong acid + weak base → acidic salt + H₂O

3. weak acid + strong base → alkaline salt + H₂O

e.g.

1. Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle H_3O^+ + Cl^- + Na^+ + OH^- \rightarrow NaCl + H_2O }

2. Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle H_3O^+ + Cl^- + NH_3 \rightarrow NH_4Cl + H_2O }

3. Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle H_3O^ + HCO_3^- + 2Na^+ + 2OH^- \rightarrow Na_2CO_3 + 3H_2O }

The chemical notation of salts is written like this:

(positive ion (cation))_x (negative ion (anion))_y • nH₂O; e.g. CaCl₂ • 6 H₂O ,

x,y,n being the number of the ions or water molecules

Salts consist of cations and anions that are bound together with ionic bonds. They are crystalline materials.

Composition of salts?

The most "damaging" and frequently found salts consist of these
anions:

• Sulphate SO₄^2-
• Nitrate NO₃-
• Chloride Cl^-
• Carbonate CO₃^2-

And the cations

• Sodium Na⁺
• Potassium K⁺
• Calcium Ca²⁺
• Magnesium Mg²⁺

other anions are:

• Acetate CH₃COO^-
  
• Formiate HCOO^-
• Oxalate C₂O₄^2-
• Phosphate PO₄^3-

further cations are:

• Ammonium NH₄⁺
  

Salt properties

Salts have certain properties that help to explain their behaviour in solution and their "damaging" effect on objects. These are:

• solubility
• deliquescence humidity

an atom or molecule with a negative electrical charge.

A molecule is an electrically neutral group of at least two atoms.

an atom or molecule with a positive electrical charge