Sulfuric acid and Potassium hydroxide Reaction | H₂SO₄ + KOH

Sulfuric acid (H₂SO₄) reacts with Potassium hydroxide (KOH) gives potassium sulfate (K₂SO₄) and water (H₂O) as products. Heat is released due to neutralization of a strong acid (H₂SO₄) and a strong base (KOH).

In this tutorial, we will discuss followings.

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Balanced reaction of H₂SO₄ and KOH

H₂SO₄ + 2KOH_(aq) → K₂SO_4(aq) + 2H₂O_(l)

One mole of H₂SO₄ reacts with two moles of KOH. As products, one mole of K₂SO₄ and two moles of H₂O are given.

Reactants of reaction

Potassium hydroxide (KOH)

Potassium hydroxide is a white solid at room temperature and readily soluble in water. Aqueous Potassium hydroxide solution is a strong base because it completely dissociates to K⁺ and OH^- ions in water as below. Due to strong basic characteristics, aqueous KOH should show pH values much higher than 7.

KOH_(aq) → K⁺_(aq) + OH^-_(aq)

Sulfuric acid (H₂SO₄)

Sulfuric acid is a strong acid because it completely dissociates to H⁺ and SO₄^2- ions in water. These sulfuric acid solutions should show pH values much lower than 7 due to its strong acidic nature.

H₂SO_4(aq) → 2H⁺_(aq) + SO₄^2-_(aq)

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Products of reaction

Potassium sulfate (K₂SO₄

Potassium sulfate is a salt and soluble in water to form a colourless aqueous solution. An aqueous solution which contains only K₂SO₄ as a salt, is a neutral solution.

K₂SO_4(aq) → 2K⁺_{(aq) + SO4^2-(aq)}

Heat generation when H₂SO₄ and KOH are neutralized

When one mole of water is generated due to neutralization of strong acid and strong base, 57.1kJ is released. Because two moles of water are generated according to the above stoichiometric balanced equation, -114.2 kJ (57.1 kJ mol^-1* 2 mol) kJ is released when H₂SO₄ is neutralized by KOH.

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Change of oxidation numbers

This reaction is not a redox reaction because oxidation numbers of atoms are not changed during the reaction.

• Potassium's only oxidation state is +1. In both KOH and K₂SO₄, potassium is at +1 oxidation state.
• Sulfur's oxidation number in H₂SO₄ is +6. And also, on KSO₄, oxidation number of sulfur is +6.

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Physical and chemical observation of H₂SO₄ and KOH reaction

Here, we will see some physical observations and chemical properties changes during the reaction.

Colour and physical state changes

• Both aqueous H₂SO₄ and aqueous KOH are colourless aqueous solutions.
• K₂SO₄ which is given as a product is readily soluble in water and give a colourless aqueous solution.

pH change

• Reactants: KOH is a strong base and show pH value higher than 7 and H²SO₄ is strong acid and should show pH value less than 7.
• Products: K₂SO₄ is a salt. Both K⁺ and SO₄^2- ions are stable in water and do not participating in hydrolysis reactions. If all H₂SO₄ and KOH are completely reacted with each other, pH of final solution should be 7.

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Safety and health hazards possible of H₂SO₄, KOH and K₂SO₄

• H₂SO₄: Causes severe skin burns,cause eye damages
• KOH: Harmful if swallowed, severe skin burns (skin corrosion and irritation) and eye damage
• K₂SO₄: Corrosive, serious eye damage, eye irritation,
• Heat generation: Due to generation of large heat in a short time period, be careful to not touch beaker or other where reaction is being happened.

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Questions

Ask your chemistry questions and find the answers

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