NaCl is the chemical formula for sodium chloride which is also commonly known as a table or common salt. It is an ionic compound that has a molecular mass of 58.44 g/mol and is composed of sodium (Na+) and chloride (Cl-) ions present in a ratio of 1:1.
The seawater contains approximately 2.7-2.9% of sodium chloride which is the major factor for the saline nature of seawater. NaCl appears to be a white crystalline solid in its pure form and makes a colorless solution when dissolved in water in which it is completely soluble.
Let us start reading our article about the ph of NaCl, and what nature it has ie; acidic, basic, or neutral.
So, what is the ph of NaCl? NaCl is a neutral compound as it has a pH value of 7. It is neither acidic nor basic in nature. NaCl is neutral as it is formed by the neutralization reaction of HCl (strong acid) and NaOH (strong base). The strong acid and strong base in the aqueous solution neutralize each other forming a neutral product ie; NaCl with ph value 7.
Let us understand the reason behind this in detail in the following context.
Why is NaCl Neutral?
A general idea behind the neutrality of sodium chloride is that the acidic, basic or neutral nature of a compound can be told easily by its pH value.
Any compound having a pH value lower than 7 will be acidic in nature, higher than 7 will be basic or alkaline in nature and equal to 7 will be neutral.
Since NaCl has a pH value of 7, it is considered to be neutral in nature.
Neutralization takes place when an acid reacts with a base and results in the formation of salt which has the properties of both the acid and the base.
NaCl is the reaction product of NaOH which is a strong base and HCl which is a strong acid.
On dissolving in water it gives a colorless neutral solution as it has an equal number of hydrogen and hydroxyl ions.
Why is NaCl neither Acidic nor Basic?
When dissolved in water, acids produce hydrogen ions which on combined with water molecules result in the formation of hydronium ions, whilst bases take up these hydrogen ions to produce hydroxide ions.
This interchange of ions is necessary for any acid-base reaction to occur.
However such exchange does not take place when NaCl is dissolved in water as it only produces the sodium and chloride ions.
These sodium (Na+) and chloride (Cl-) ions are weak conjugate acid and conjugate base respectively and therefore they don’t have enough intensity to impart acidic or basic behavior to the solution.
Also, these ions balance each other out to make a neutral salt solution.
pH Calculation of NaCl
The pH of solid NaCl can be calculated easily by dissolving it in water in small quantities.
On dissolving completely, it produces sodium ions (Na+) and chloride ions (Cl-).
This dissociation is represented by the following equation;
NaCl(s) —-> Na+(aq) + Cl-(aq)
Both the sodium and chloride ions do not react with the water molecules.
This is because the sodium ions react with water molecules to produce sodium hydroxide which is a strong base, so it ultimately dissociates into sodium ions back again.
The following two reactions represent this;
Na+(aq) + H2O(l) ⇋ NaOH(aq) + H+(aq)
NaOH(aq) → Na+(aq) + OH-(aq)
Similarly the chloride ions on reacting with water form hydrochloric acid which is a strong acid, so it too dissociates into chloride ions back again, as can be seen in the following two equations;
Cl-(aq) + H2O(l) ⇋ HCl(aq) + OH-(aq)
HCl(aq) —–> H+(aq) + Cl-(aq)
Therefore when a salt of a strong acid and strong base like sodium chloride is dissolved in water, the respective conjugate acid and base do not contribute to the pH of the final solution.
The only ions contributing to the final pH value are the ones dissociated by water, i.e the hydrogen and hydroxide ions respectively.
The auto-ionization of water can be seen in the following chemical equation:
H2O(l) ⇋ H+(aq) + OH-(aq)
The ionic product of water (Kw) for this equation would look something like
Kw = [H+(aq)][OH-(aq)]
And we know that the hydrogen ion concentration is equal to the hydroxide ion concentration in the case of water, i.e [H+(aq)] =[OH-(aq)]
Therefore, the ionic product equation would format itself to;
Kw = [H+(aq)]2
And this gives us the hydrogen ion concentration which will be equal to the square root of the ionic product of water.
And as we know that at 25°C, Kw = 10-14, therefore the hydrogen ion concentration will be equal to 10-7 mol L-1.
[H+(aq)] = √Kw = √10-14 = 10-7 mol L-1
Now, pH is calculated by taking the negative of the log of hydrogen ion concentration. Then this will gives us the
pH = −log10[H+(aq)]
pH = −log10[10-7] = 7
Therefore, by the calculations, it is proved that the pH of sodium chloride when dissolved in water at room temperature i.e at 25°C, is equal to 7.
Structure of NaCl
As NaCl is an inorganic compound, its structure cannot be explained by the rules used to understand the structures of organic compounds.
NaCl has a rock salt crystal structure with a face-centered cubic Bravais lattice.
It is formed by repeating the face-centered cubic unit cells and each unit cell has the ratio of Na+ and Cl-ions as 1:1.
The meaning of the 1:1 ratio means that the no. of Na+ cations equals the no. of Cl- anions.
The Chloride ions are present inside the lattice in the CCP type of arrangement which means that these are at the corners and at the face centers of the cube.
Whereas the sodium ions are present in a way that there are six chloride ions surrounding it or we can say that the sodium ions occupy all the octahedral voids.
It can be seen in the diagram that each chloride anion has six sodium cations surrounding it and vice versa making what looks like a regular octahedron.
This also means that the cations and the anions are present in the structure having a coordination ratio of 6:6 and each unit cell contains four cations and four anions making a total of eight ions all together in one unit cell.
A single unit call has the Lattice constant (a) of 0.564nm and the lattice parameters; 1) sides i.e (a=b=c) and 2) angles i.e (α=90∘,β=90∘,γ=90∘).
You must refer to the article I wrote on is NaCl ionic or covalent.
● Sodium chloride has a density of 2.16 g/mL, a boiling point of 1465°C, and a melting point of 801°C.
● It doesn’t have any characteristic smell but contains a characteristic taste of its own.
● It is completely soluble in water and other polar solvents, however, it is only partially soluble and insoluble in other kinds of liquids.
Its aqueous solution is called saline solution and it can have varying concentrations.
● It decomposes at a high range of temperature and produces toxic fumes of hydrochloric acid (HCl) and disodium oxide (Na2O) while decomposing.
● It is known for being a good conductor of electricity in the aqueous state because of the free movement of the ions in the solution.
Sodium chloride finds its applications in various sectors some of which are;
● It is widely used as a food preservative as well as for the purpose of adding flavor to food items.
● It is a valuable raw material used to manufacture chemical compounds like sodium carbonate (Na2CO3), sodium hydrogen carbonate (NaHCO3), baking soda, hydrochloric acid, etc. as well as in the manufacturing of glass.
● In countries that experience snowfall every year during the winter season, it is used to stop the building up of snow on-road tracks, bridges, railway tracks, etc which is necessary for driving and walking safely.
● It is a common industrial material to be used in the industries of oil refineries, textiles, fire-retardants, rubber, etc.
● It is an important substance for the human body to maintain its electrolyte balance of fluids. If the levels drop too low or go up too high, it can make a person dehydrated or over hydrated.
● In the human body, NaCl functions in the transportation and absorption of nutrients, maintaining hydration and blood pressure, and many more.
To summarise, NaCl is what we all are familiar with since we use it on an everyday basis to add flavor to our food. It has a rock salt structure as discussed in detail earlier.
It appears to be a white crystalline solid and makes a colorless solution when dissolved in water. It is a neutral compound and has a pH scaling of 7.
It is a reaction product of sodium hydroxide and hydrochloric acid. It has a huge number of applications in the industrial and the health sector some of which were discussed in the context.
We have one similar article on a similar salt ie; KCl. Check out is KCl ionic or covalent.