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 %.
The opposite type of reaction (where energy is taken in from the surroundings of a reaction and thus the energy of the reactants is lower than that of the products) is called an endothermic reaction
Answer:
NH4)3PO4
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Answer:
Elements in same column of periodic table have same properties.
Explanation:
The elements in the same group have same number of valance electrons thus have similar properties.
Consider the elements of group two i.e alkaline earth metals. All have two valance electrons and show similar properties.
Magnesium, barium, calcium etc.
All alkaline earth metals form salt with halogens.e.g,
Mg + Cl₂ → MgCl₂
Ba + Br₂ → BaBr₂
Mg + Br₂ → MgBr₂
Ca + Br₂ → CaBr₂
They react with oxygen and form oxides of respective metal.
2Mg + O₂ → 2MgO
2Ba + O₂ → 2BaO
2Ca + O₂ → 2CaO
these oxides form hydroxide when react with water,
MgO + H₂O → Mg(OH)₂
BaO + H₂O → Ba(OH)₂
CaO + H₂O → Ca(OH)₂
With nitrogen it produced nitride,
3Mg + N₂ → Mg₃N₂
3Ba + N₂ → Ba₃N₂
3Ca + N₂ → Ca₃N₂
With acid like HCl,
Mg + 2HCl → MgCl₂ + H₂
Ba + 2HCl → BaCl₂ + H₂
Ca + 2HCl → CaCl₂ + H₂
