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Sodium bisulfate is a sodium salt of bisulfate anion with the chemical formula NaHSO4. It is an acidic salt, whose each 1M solution is 1 pH. Sodium bisulfate is produced when an equivalent amount of sodium base partially neutralizes the sulphuric acid. It is a white and dry granular substance, hygroscopic in an anhydrous state, very corrosive to tissues and metals, and is soluble in water.
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What is NaHSO4?
Sodium chloride or sodium hydroxide (lye) are the two most common forms of sodium bisulfate. In the industrial Mannheim process, sodium bisulfate is generated when sodium chloride reacts with sulphuric acid. The chemical equation of the Mannheim process is-
NaCl + H2SO4 → HCl + NaHSO4
As NaHSO4 is very poisonous to some echinoderms but non-toxic to most other living organisms, it is used to suppress the crown-of-thorns starfish infestations.
The IUPAC name of sodium bisulfate is- Sodium hydrogen sulfate. It is also known as sodium acid sulfate and bisulfate of soda.
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One of the crucial chemical reactions of sodium bisulfate occurs at a temperature of 60°C. In this, the hydrated sodium bisulfate dehydrates first. Next, the water molecule that is connected to it separates. The compound is now allowed to cool down. The cooling compound is re-heated at 290 °C, forming a colorless salt of sodium pyrosulphate. The chemical reaction that occurs in this process is-
2 NaHSO4 → Na2S2O7 + H2O
Properties of Sodium Bisulphate – NaHSO4
| NaHSO4 | Sodium bisulphate |
|---|---|
| The molecular weight of NaHSO4 | 120.06 g/mol (anhydrous) 138.07 g/mol (monohydrate) |
| Appearance | White solid |
| The density of Sodium bisulphate | 2.742 g/cm3 (anhydrous) 1.8 g/cm3 (monohydrate) |
| The boiling point of Sodium bisulphate | decomposes to Na2S2O7 (+ H2O) at 315°C (599°F; 588 K) |
| The melting point of Sodium bisulphate | 58.5°C (137.3°F; 331.6 K) (monohydrate) 315°C (anhydrous) |
| Solubility in water | 28.5 g/100 mL (25°C) 100 g/100 mL (100°C) |
| Solubility | Insoluble in ammonia |
| Acidity (pKa) | 1.99 |
Check Important Notes for Ideal and Non-Ideal Solution
NaHSO4: Physical Properties
- Anhydrous (dry) sodium bisulfate (NaHSO4) and monohydrate (NaHSO4.H2O) are two common forms of sodium bisulfate.
- Anhydrous NaHSO4 is a type of white powder that is shapeless and hygroscopic, having a density of 2.74 g/mL.
- The melting point of the compound is recorded to be 315°C
- The monohydrate is a sandy white-colored solid with a melting point of 59°C and a 1.8 g/mL density.
- It is regarded as safe for shipping and storage purposes.
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NaHSO4: Chemical Properties
- Sodium bisulfate (NaHSO4) is a water-soluble compound.
- Since only a single acidic proton of diprotic sulphuric acid is substituted during the reaction, it is a non-normal neutral salt. Instead, it is an acidic salt.
- NaHSO4 is highly acidic in its aqueous state.
- It reacts vigorously with strong bases and strong oxidizing agents.
- Under normal circumstances and conditions, it is stable. However, when exposed to water, it decomposes, or more precisely, it dissolves in water.
Structure of NaHSO4
The sodium bisulfate molecule (sodium hydrogen sulfate molecule) consists of a positively charged sodium cation and a negatively charged bisulfate anion that forms an ionic bond in its molecule structure.
To be precise, sodium acid sulfate has a mass of 119.949 g/mol, the same as the monoisotopic mass of the salt. The number of hydrogen bond acceptors is four, but the number of hydrogen bond donors is only one in sodium bisulfate compounds. This chemical compound has two covalently bound units, which are canonicalized.
Preparation of NaHSO4
Sodium Bisulphate, NaHSO4 can be prepared via the following process:
Step 1: The Mannheim process, which involves the interaction of sodium chloride with sulphuric acid, produces sodium bisulfate as an intermediate. This process is highly exothermic. The chemical reaction is-
NaCl + H2SO4 → HCl + NaHSO4
Step 2: The liquid form of sodium bisulfate is sprayed and allowed to cool until it solidifies into a bead structure. Hydrochloric acid is generated as an essential co-product when the hydrogen chloride gas is dissolved in water.
Step 3: Although sodium bisulfate is not of much economic interest, it can be produced as a by-product of the synthesis of many other mineral acids by reacting their sodium salts with excess sulphuric acid. The reaction occurring during this stage is-
NaX + H2SO4 → NaHSO4 + HX (X− = CN−, NO3−, ClO4−)
Step 4: Distillation separates the acids HX generated from the reaction because they have a lower boiling point than the reactants involved in the above-stated reaction. The final product extracted is the sodium bisulfate compound.
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Applications of NaHSO4
Sodium bisulfate is commonly used as:
- Preservative
- Food additive
- Medicinal ingredient
- Nutritional supplements
- pH controls
- Products used for household cleaning
- Tanning of leather
- Disinfecting agent
- Swimming pools
- Cleaning of metals
- In the finishing of metal
- In paints
- manufacturing of paper products
- In chicken house to reduce the concentration of Salmonella
- agricultural chemicals
- velvet cloths
- bleaching agent
- in water treatment products
- a catalyst
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NaSO4: Health Hazards
Sodium hydrosulphite is a poisonous, caustic, and non-flammable substance. Inhalation, ingestion, or skin contact with sodium bisulfate can result in severe harm or even death. In addition, it releases unpleasant and poisonous fumes when heated.
Things to Remember
- The pH of 1M solution 1. As a result, it is used to balance the pH of basic substances.
- Sodium bisulfate is also known as sodium acid sulfate and bisulfate of soda.
- A positively charged sodium cation and a negatively charged bisulfate anion in the sodium bisulfate compound are attached by an ionic bond.
- Sodium pyrophosphate is a colorless inorganic salt.
- The formula of sodium pyrosulfate compound is Na2S2O7.
- It is mainly used in analytical chemistry and quantitative analysis.
- Sodium bisulfate (NaHSO4) is a water-soluble compound because it is hygroscopic, meaning it attracts water towards itself.
- The acid strength (pKa) of sodium bisulfate is 1.99, which means it is a strong acidic salt. Sodium bisulfate irritates the eyes and causes rashes and burns on the skin if it comes in contact with these sensitive areas.
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Sample Questions
Ques: NaHSO4 is a salt. However, it is slightly acidic. Why? (2 marks)
Ans: NaHSO4 dissociates completely in the water as Na+ and HSO4- ions.
The HSO4- ion once again dissociates with water to form H3O+ ion and SO42- ion
The overall reaction is as follows:
NaHSO4 (s) + H2O(l) → Na+(aq) + SO42-(aq) + H3O+
Ques: Why when NaCl reacts with H2SO4, NaHSO4 is formed and not Na2SO4? (3 marks)
Ans: The production of the product is dependent on the temperature provided. At 420K, NaCl + H2SO4 gives NaHSO4, whereas, at 823K, the NaHSO4 formed in the reaction reacts again with the NaCl to give Na2SO4.
Ques: Are acidic salts like NaHSO4 and KHCO3 acids or salts? (3 marks)
Ans: Both NaHSO4 and KHCO3 can be classified as salts. They are generated when dibasic acids, such as H2SO4 and H2CO3, are partially neutralized by the alkalis NaOH and KOH, respectively. Because they don't liberate H+ ions in an aqueous solution, they can't be considered acids. KHCO3 ionizes into K+ and HCO3- ions, while NaHSO4 ionizes into Na+ and HSO4- ions. In water, the bicarbonate ion also hydrolysis to produce OH- ions.
Read More: Acid, Bases, and Salts
Ques: Which type of salt is NaHSO4? (3 marks)
Ans: Because it includes one replaceable hydrogen, sodium hydrogen sulfate (NaHSO4) is classified as an acid salt. When more sodium hydroxide is added to this intermediate salt (complete neutralization), sodium sulfate (Na2SO4) is formed, the 'normal salt' of sulphuric acid and sodium hydroxide.
NaOH + H2SO4 = NaHSO4 (acid salt) + H2O ……. (Partial neutralisation)
NaHSO4 + H2SO4 = Na2SO4 (normal salt) + H2O ……. (Complete neutralisation)
NaHSO4 is also known as an 'acidic salt,' since its aqueous solution is highly acidic.
Ques: Is NaHSO4 a metal hydride? (2 marks)
Ans: It's not a hydride. Only the metal ion and the hydrogen ion make up the hydride. Furthermore, unlike this, where the hydrogen is in a positive oxidation state, a hydride is negative.
Ques: What is the oxidation number of S in NaHSO4? (4 marks)
Ans: +6
Each of the four oxygens has a cumulative charge of -8(which is -2). The charge of H and Na is +1, and the overall charge of the molecule is 0. Simple arithmetic is used to solve the problem.
H + Na + S + 4(O) =0
(+1) + (+1) + x +4(-2) =0
X = 0 - (-6)
X = +6
Read More: Acid, Bases, and Salts
Ques: Is NaHSO4 an ionic or a covalent bond? (2 marks)
Ans: NaHSO4 has an ionic bond because it is produced when Na gives one electron to HSO4 (hydrogen sulfate) to form Na+ and HSO4-, which then combine to form NaHSO4 by gaining lattice energy (Sodium bisulfate).
Ques: Why is NaHSO4 called acidic salt? (3 marks)
Ans: It is generated when NaOH and Conc.H2SO4 are partially neutralized. When NaHSO4 is dissolved in water, it produces H+ ions because it possesses a replaceable H+ ion.
NaOH + H2SO4------> NaHSO4 + H2O
It's because of this that it's referred to as an acidic salt.
Ques: What happens if you mix NaHSO4 and acetic acid? (2 marks)
Ans: HSO4- is amphoteric, meaning it can act as both an acid and a base. Because acetic acid is the stronger acid, HSO4- behaves as a base, resulting in an acid-base reaction.
NaHSO4 + CH3COOH → CH3COO- Na+ + H2O
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