Hydrogen Sulfate

Hydrogen sulfate also commonly known as bisulfate is an anion. The hydrogen sulphate formula is given by HSO4-. Hydrogen sulfate is formed with the chemical radical sulfate (HSO4). When HSO4 are exposed to water, they react to form Sulfuric Acid (H2SO4). With the Sulfate radial, hydrogen sulfates are generally acidic in nature. In fact, they are used as a weaker alternative to Sulfuric acid. Hydrogen sulfate reacts with Sodium to form Sodium Bisulfate (NaHSO4) which is actually a pure substance. It creates a tetrahedral arrangement with the Sulfur atom at the center and four Oxygen atoms surrounding it. It forms a structure similar to that of Methane. 

Structure of Hydrogen Sulfate

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Physical Properties of Hydrogen Sulfate

Chemical Formula of hydrogen sulfate


Molar Mass



1826.7 kg/m3

Melting Point

59o C





Reactive With

Water, Nitric Acid, Ethanol, Acetone

Chemical Properties of Hydrogen Sulfate

Some of the chemical properties of Hydrogen Sulfate are given below:

  • Hydrogen sulfate is highly reactive with distilled water, forming sulfate and hydronium ions. Its chemical equation is given by: 

HSO4 + H2O → H3O+ + SO42- 

  • It can also react with nitrate ion, in order to form sulfate ion and nitrous acid. The chemical equality is down below: 

HSO4 + NO2 → SO42- + HNO2

  • Hydrogen sulfate can also react with water (as a base) and form hydronium ions. This happens as per the Brønsted-Lowry Acid-Base Reactions.


As per the Brønsted-Lowry, an acid-base reaction actually occurs when there is a transfer of one proton from one ion or molecule to another. In the above case, water acts as a base since it reacts with HSO4, which is a better proton donor. This happens due to the amphoteric nature of water. It can act both as a base and acid.

Hydrogen Sulfate Uses

Some of the major use cases of Hydrogen sulfate are given below:

  • It is mainly used in the water treatment plants in order to remove any residual chlorine. Hydrogen sulfate is one of the major alternatives to liquid sulfur dioxide

  • The production of niter cake is done with the help of sodium salts of hydrogen sulfate

  • The resins formed from hydrogen sulfate are heavily used to soothe the skin

What is Sulfate?

Sulfate with its chemical formula, SO42-  is actually a sulfur oxoanion. By deprotonation of both the OH group in Sulfuric acid, one can actually obtain the sulfate radical. 

What is Strong and Weak Acid?

Based on the pH level of the compound, one can actually determine whether it is a strong acid or a weak one. On the scale of 0 -14, the pH level decreases, the acidic nature increases. In fact, in some strong acids like HCL, the pH can even go below 0. Strong acids get completely dissociated in water. However, weak acids only get partially dissociated in water.

What are the Differences Between Hydrogen Sulfate and Hydrogen Sulfide?

Hydrogen sulfide can be easily identifiable. It has a distinct odor that resembles the smell of rotten eggs. It is produced after the decomposition of animal and plant tissue. High concentrations of it can be quite toxic and is very corrosive to metal objects. It even has the potential to corrode stainless steel. Hydrogen sulfate is also another form of sulphur. However, unlike hydrogen sulfide, it does not produce gas and does not contain odor. It occurs naturally in minerals like rocks, soils and sediments. Sulfate can be harmful for our health too. High levels of sulfate consumption can act as a laxative and that can cause dehydration in human beings. 

Solved Questions

Example 1

How to find the oxidation number of S in hydrogen sulfate?

From the formula of hydrogen sulphate, we know that it is HSO4-

According to the general rule of oxidation number,

  • All the oxidation number must add up to the charge of the ion

  • The oxidation number of H is 1

  • The oxidation number of O is -2

So, According to the question,

1 + S + (-2) * 4 = -1

S = 6, So the oxidation number of Sulfur is 6 in hydrogen sulfate.


Example 2

We all know that hydrogen sulfate or HSO4 acts as either a base or acid in water. So, in which of the following equations, hydrogen sulfate acts as an acid, and why? 

1) HSO4+ H2O = H2SO4  + OH-

2) HSO4+ OH- = H2SO4 + O2-

3) HSO4+ H2O   = SO42-N + H3O -

4) HSO4+ H3O - = SO3 + 2H2O

The answer is option 3. Here HSO4is actually acting as an acid because of the H+ ion that it gives away. As for the other equations, HSO4 name is acting as a base, either giving away OH-  or taking H+ ion.

FAQ (Frequently Asked Questions)

1. Why is the HSO4 Formula Often Called Hydrogen Sulfate Instead of Hydrogen Persulfate?

Hydrogen sulfate is one of the oxyanions, which means that it incorporates a single negative change along with an oxygen atom. One of the properties of hydrogen sulphate is that its central sulfur atom is actually joined with three oxygen atoms along with one hydroxyl group. The term sulfate is used instead of persulfate, because instead of a peroxide unit linked with the sulfur there is a hydroxyl group.

2. What are the Differences Between Hydrogen Sulfate and Sulfuric Acid?

We all know that the hydrogen sulphate formula is given by HSO4-, whereas dihydrogen sulfate also known as sulfuric acid has a formula, H2SO4. This let alone states the fact that hydrogen sulfate and sulfuric acid are two different chemicals. Neither less to say, both of them are acids. Yet, hydrogen sulfate is often used as a weaker alternative to sulfuric acid. The acidic nature of hydrogen sulfate is formed due to the electronegative oxygen that isolates the electron density.