Is NaCN a base or an acid?

Sodium cyanide is a crystalline white substance that is water soluble. It’s a sodium hydroxide and hydrogen cyanide salt. It’s also known as sodium cyanide, Cyanobrik, or Cyanogran. It’s extremely harmful since it messes with the body’s metabolic processes.

It dissociates into cyanide anions and sodium cations in an aqueous solution. The Castner process, in which sodium amide combines with carbon at high temperatures, is used to make sodium cyanide.

The chemical reaction is as follows:

NaNH2  +  C  →  NaCN  +  H2

Is NaCN an acid or a base, then? A basic is sodium cyanide. It’s a basic salt created when a strong base, sodium hydroxide (NaOH), reacts with a weak acid, hydrogen cyanide (HCN). The salt of a weak acid and a strong base is basic in nature, as we already know. As a result, NaCN is fundamental. It also has a pH of greater than 7, ranging from 10 to 11, and a Ka value of 4.9 X 10-10, indicating alkalinity.

The basicity of Sodium Cyanide (NaCN) and its basics will be discussed in this article.

What makes NaCN such a basic salt?

The direct interaction between sodium hydroxide and hydrogen cyanide produces sodium cyanide.

The following is the reaction equation for making sodium cyanide:

HCN (acid)  +  NaOH (base)   —->   NaCN (salt)  +   H2O

A neutralisation reaction occurs when an acid combines with a base to form salts, and the nature of the salt formed as a result of such reactions is determined by the strength of the acid and base used as reactants.

The following is a simple rule for determining the nature of the neutralisation reaction product:

Acidic salt (pH 7) is formed by combining a strong acid and a weak base. Examples include NH4Br, NH4NO3, and others.

Basic salt (pH > 7) is made up of a weak acid and a strong base. Examples include NaCN, Na2CO3, and others.

Strong acid + strong base = neutral salt with a pH of 7; examples include NaCl, KCl, and others.

Because we already know that HCN is a weak acid and NaOH is a strong base, the product of their neutralisation reaction, NaCN, is a basic salt.

What makes NaCN a non-acidic salt?

In an aqueous solution, an acid is defined as a chemical that creates protons.

They should turn blue litmus red and have a pH of less than 7. The following theories can be used to classify a chemical as an acid or a base:

• Bronsted-Lowry Theory: Johannes Bronsted and Thomas Lowry presented the Bronsted-Lowry Theory, sometimes known as the proton theory, in 1923.

According to this idea, acids are compounds that may transmit their protons to other molecules.

• G.N. Lewis proposed the Lewis Theory in 1923. Acids are the acceptors of unshared electron pairs, according to this idea.

• Svante Arrhenius proposed the Arrhenius Theory in 1887. Acids are chemicals that dissociate to form hydrogen ions, according to the theory.

Let’s look at the dissociation equation for sodium cyanide, taking into account the postulates of these theories:

NaCN    —>    Na+   +   CN-

The NaCN molecules dissolve to create Na+ ions, which are incapable of further reaction, and CN- ions, which would rather take a proton or give away a lone pair of electrons, as shown in the above reaction equation.

As a result, when sodium cyanide molecules dissociate, they are unable to produce hydrogen ions or protons, nor are they able to take unshared electrons.

As a result, sodium cyanide can’t be classified as an acid.

Check if NaCl is basic, acidic, or neutral, as it is a very similar chemical.

Why is the NaCN aqueous solution basic?

As seen in the preceding section’s reaction equation, sodium cyanide molecules breakdown into sodium and cyanide ions.

Let’s go over the conjugate acids and bases laws again:

When a strong acid reacts with a weak conjugate base, the result is invariably a weak conjugate base.

When a weak acid reacts with a strong conjugate base, the result is invariably a strong conjugate base.

When a strong base reacts with a weak conjugate acid, the result is invariably a weak conjugate acid.

When a weak base reacts with a strong conjugate acid, the result is invariably a strong conjugate acid.

Looking at the sodium cyanide molecules once more, we can see that they are made up of a strong basic, sodium hydroxide, and a weak acid, hydrogen cyanide.

As a result, the Na+ produced is the weak conjugate acid of the strong base, which does not hydrolyze further and hence has no influence on the solution’s pH.

However, because the CN- ion is a strong conjugate base of a weak acid (HCN), it hydrolyzes further by accepting a proton from a water molecule, releasing OH- ions into the water.

The following is the chemical equation:

CN-   +    H2O    —–>    HCN   +    OH-

The basicity of the sodium cyanide aqueous solution is due to these hydroxyl ions.

Do you believe NaCN to be a strong or weak base?

NaCN is a salt that should not be classified as an acid or a basic. It’s the result of an acid and a base reacting to neutralise each other.

We must remember the ground rule in the case of salt, which was described in the previous section.

A salt generated by reacting a strong base with a weak acid always has a pH greater than 7, indicating that it is basic.

As a result, sodium cyanide is classified as a basic salt.

If solely pH and Ka values are used to determine the strength of sodium cyanide as a base, it is a strong basic chemical because its pH is substantially higher than 7, between 10 and 12, and its Ka value is 4.9 X 10-10.

NaCN’s pH

The pH value of a substance is used to determine its acid or basic nature and strength.

The pH scale ranges from 1 to 14, with acids having a pH value less than 7 and bases having a pH value greater than 7.

The pH value of neutral substances, such as water, is said to be 7.

Let’s compute the pH of a 0.1 M NaCN solution. The solution’s Ka value is stated as 4.9 X 10-10. The chemical formula is as follows:

CN-   +   H2O    —>    HCN   +   OH-

We are aware of this. 10-14 = Ka X Kb

Kb = 10-14/4.9 X 10-10 as a result.

= 2.04 X 10-5 = 2.04 X 10-5 = 2.04 X 10-5

Using the aforementioned chemical equation to calculate the concentration of OH- ions, we can see that

Kb = ([HCN] [OH-]) / [CN-]

As a result, 2.04 X 10-5 = x2/0.1 – x2.

As a result, [OH-] = x = 1.43 X 10-3

Now that we are aware of this, pOH = -log [OH-] pOH = -log [OH-] pOH = -log

-log = (1.43 X 10-3)

2.84 =

Furthermore, pH + pOH = 14

14 – 2.84 = 11.15 pH

As a result, the pH of 0.1 M NaCN solution is 11.15, which is significantly higher than 7, showing that it is a basic salt.

Properties

The following are some of sodium cyanide’s most important properties:

• It’s a sodium hydroxide/hydrogen cyanide salt.

• The chemical formula for this substance is NaCN.

• The molecular weight of this compound is 49.0072 gm/mol.

• It has a density of 1.59 grammes per cubic centimetre.

• In aqueous solution, it is a white crystalline solid that appears colourless.

• It has a subtle almond scent to it.

• The melting and boiling points of sodium cyanide are 563.7 and 1496 degrees Celsius, respectively.

• It can be dissolved in water as well as other solvents such as methanol, ethanol, and ammonia.

• It has a 1.452 refractive index.

• It’s a highly toxic substance.

• It is not flammable.

• Some metals, like as aluminium, are corroded by it.

• It has a pH greater than 7 and is an alkaline salt.

• The sodium and cyanide ions are in a 1:1 ratio in a NaCN molecule.

• It is deliquescent, which means it collects water from the air and converts it to a liquid.

Uses

The following are some of sodium cyanide’s most important applications:

• Because cyanide has a strong affinity for gold, it is employed in gold extraction. The response is written as follows:

4Au + 8NaCN + O2 + 2H2O   —–>    4Na[Au(CN)2] + 4NaOH

• Cyanide is utilised in the manufacture of nitriles, especially medicines, due to its strong nucleophilic tendency.

• Entomologists utilise it for their collection jars due to its very toxic properties.

• Sodium cyanide is also employed as a test reagent for determining the function of chemoreceptors.

• It is also utilised in the dyeing process.

• Because it is poisonous, it is also used as a rodenticide.

• It’s used for cleaning metals as well as making electroplating solutions.

• Hydrocyanic acid is made with sodium cyanide.

• It can be utilised as a chelating agent as well.

• In agricultural fields, sodium cyanide is employed as a pesticide or insecticide.

Conclusion

A neutralising reaction between a strong base, sodium hydroxide, and a weak acid, hydrogen cyanide, produces sodium cyanide, a basic salt.

It does not produce protons or hydrogen ions, nor does it receive unshared pairs of electrons, hence it does not fit into any of the theories of acids and bases’ definitions of acids.

Because the interaction between cyanide ions and water produces hydroxyl ions, the aqueous solution of NaCN is basic.

For a 0.1 M solution of NaCN, the pH and Ka values are 11.15 and 4.9 X 10-10, respectively.

If you have any further questions, please post them in the comments section and share this information with your friends.

Good luck with your studies!!

Read more: Strong or Weak Intermolecular Forces in HCl?

Misha Khatri
Misha Khatri is an emeritus professor in the University of Notre Dame's Department of Chemistry and Biochemistry. He graduated from Northern Illinois University with a BSc in Chemistry and Mathematics and a PhD in Physical Analytical Chemistry from the University of Utah.

LEAVE A REPLY

Please enter your comment!
Please enter your name here

Read More

Recent