When barium sulphate (BaSO₄) is heated strongly with carbon (coke/charcoal) at high temperatures, it undergoes reduction to form barium sulphide (BaS) and carbon monoxide (CO). The reaction is: BaSO₄ + 4C → BaS + 4CO↑. This industrial reaction is used to prepare barium sulphide from barite (natural BaSO₄), which is the starting material for producing other barium compounds.
Barium sulphate + carbon: BaSO₄ + 4C → BaS + 4CO↑ (at ~1000–1200°C).
Carbon is the reducing agent; BaSO₄ is reduced to BaS.
BaSO₄ is very stable (Ksp = 1.1 × 10⁻¹⁰) and requires high temperature for reduction.
Products: barium sulphide (BaS) and carbon monoxide (CO).
BaS is soluble and reactive — used to make other barium compounds (BaCl₂, BaCO₃, Ba(OH)₂).
Barite (natural BaSO₄) is the main ore — carbon reduction is the industrial route to barium chemicals.
BaSO₄ is used in medical X-ray imaging because it is non-toxic and insoluble in body fluids.
CO is the main gas product at high temperatures (Boudouard equilibrium).
Chemical equation: BaSO₄ + 4C → BaS + 4CO↑
Word equation: Barium sulphate + Carbon (coke) → Barium sulphide + Carbon monoxide
Conditions: • Temperature: ~1000–1200°C (high temperature required) • Carbon acts as a reducing agent (C is oxidised from 0 to +2 in CO) • BaSO₄ is reduced (S⁶⁺ in SO₄²⁻ is reduced to S²⁻ in BaS)
Type of reaction: • Reduction of BaSO₄ by carbon • Redox reaction: C is oxidised, S in BaSO₄ is reduced
Note: At very high temperatures, CO₂ may also be produced: BaSO₄ + 2C → BaS + 2CO₂ But at the high temperatures used industrially, CO is the main product (Boudouard equilibrium favours CO above ~700°C)
Barium sulphate (BaSO₄) is: • Extremely insoluble in water (Ksp = 1.1 × 10⁻¹⁰) • Very stable compound — high lattice energy • Does not react with dilute acids • Resistant to most reducing agents at low temperatures
This stability is why:
The carbon reduction converts stable BaSO₄ to the more reactive BaS: BaS dissolves in water and acids → allows preparation of other barium compounds BaSO₄ + 4C → BaS + 4CO
Industrial importance: The BaSO₄ → BaS conversion is the key step in barium chemistry because: • Barite (BaSO₄) is the main natural ore of barium • BaSO₄ itself is unreactive — difficult to convert directly to other compounds • BaS (barium sulphide) is soluble and reactive — used as an intermediate
From BaS, other barium compounds are made: • BaCl₂: BaS + 2HCl → BaCl₂ + H₂S • Ba(OH)₂: BaS + H₂O → Ba(OH)₂ + H₂S (with steam) • BaCO₃: BaS + CO₂ + H₂O → BaCO₃↓ + H₂S
Uses of BaSO₄: • Medical imaging: barium meal for X-ray of digestive tract • Paint pigment: blanc fixe (white pigment) • Drilling fluid in oil wells • Heavy additive in plastics and rubber
Uses of BaS: • Manufacture of BaCl₂, BaCO₃, Ba(OH)₂ • Depilatory creams (removes hair chemically)
When barium sulphate (BaSO₄) is heated with carbon (coke) at high temperature (~1000–1200°C), it is reduced to barium sulphide (BaS) and carbon monoxide (CO): BaSO₄ + 4C → BaS + 4CO↑. Carbon acts as the reducing agent.
BaSO₄ + 4C → BaS + 4CO↑. Barium sulphate reacts with 4 moles of carbon to give 1 mole of barium sulphide and 4 moles of carbon monoxide. High temperature (1000–1200°C) is required.
Barium sulphate is extremely stable and almost insoluble (Ksp = 1.1 × 10⁻¹⁰). Its high lattice energy and strong S–O bonds make it resistant to most reagents at low temperatures. Strong reducing agents like carbon (coke) at very high temperatures (~1000°C) are needed to break the sulphate bonds.
Barium sulphate is used as a contrast agent in X-ray imaging (barium meal) because it is opaque to X-rays and, importantly, completely insoluble and non-toxic. Since it does not dissolve in digestive fluids, it does not release toxic Ba²⁺ ions into the bloodstream.
Barite (BaSO₄) is the main natural ore of barium but is too stable to react directly. Converting it to BaS (soluble and reactive) allows the manufacture of all other barium compounds. From BaS: BaCl₂, BaCO₃, Ba(OH)₂ can be made. The BaSO₄ + 4C → BaS + 4CO step is the starting point of barium industrial chemistry.
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