What are acids ? Will they harm skin
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When mixture of NaCl and Al₂(SO₄)₃ is allowed to react with excess NaOH, only Al₂(SO₄)₃ reacts with it and NaCl does not react with NaOH due to presence of common ion (Na⁺). On reaction gelatinous precipitate of aluminium hydroxide [Al(OH)₃] is produced. The balanced chemical reaction is represented as-
Al₂(SO₄)₃ + 6NaOH → 2Al(OH)₃ + 3Na₂SO₄
On this reaction, 0.495 g = 0.495/78 moles =6.346 X 10⁻³ moles of Al(OH)₃.
As per balanced reaction, two moles of Al(OH)₃ is produced from one mole Al₂(SO₄)₃. So, 6.346 X 10⁻³ moles of Al(OH)₃ is produced from (6.346 X 10⁻³)/2 moles=3.173 X 10⁻³ moles of Al₂(SO₄)₃= 3.173 X 10⁻³ X 342 g of Al₂(SO₄)₃=1.085 g of Al₂(SO₄)₃.
So, mass percentage of Al₂(SO₄)₃ is= (amount of Al₂(SO₄)₃/total amount of mixture)X100 = =74.8 %.
Answer: Option (b) is the correct answer.
Explanation:
In a chemical reaction, the bonds between the reactant molecules tend to break leading to the formation of new bonds to produce products.
So, in order to break the bonds between the reactant molecules, energy is required to overcome the attraction between the atoms.
To form new bonds, energy gets released when two atoms come closer to each other. Hence, formation of bond releases energy.
As in the given reaction it is shown that < 0, that is, enthalpy change is negative. Hence, energy is released as it is an exothermic process.
Thus, we can conclude that the statement energy released as the bonds in the reactants is broken is greater than the energy absorbed as the bonds in the products are formed, is true about the bond energies in this reaction.