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The heat of reaction of both the reactions 2 KOH H2SO4 → K2SO4 2H20 and Mg(OH)2 H2SO4 → MgSO4 2 H2O is -27.2 kcal/mol. Hence the heat of reaction of 3 Ca(OH)2 2 H3PO4 → Ca3(PO4)2 6 H2O would be (A)-13.6 kcal/mol (B)-27.2 kcal/mol (C)-81.6 kcal/mol (D) -68.0 kcal/mol​?
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The heat of reaction of both the reactions 2 KOH H2SO4 → K2SO4 2H2...
Given:
The heat of reaction for the reactions:
1) 2 KOH + H2SO4 → K2SO4 + 2 H2O
2) Mg(OH)2 + H2SO4 → MgSO4 + 2 H2O
is -27.2 kcal/mol.

To find:
The heat of reaction for the reaction:
3 Ca(OH)2 + 2 H3PO4 → Ca3(PO4)2 + 6 H2O

Solution:
The heat of reaction is a measure of the energy released or absorbed during a chemical reaction. It can be calculated using the principle of Hess's law, which states that the overall enthalpy change in a reaction is independent of the pathway taken.

Hess's Law:
Hess's Law states that if a reaction can be expressed as the sum of two or more reactions, then the heat of reaction for the overall reaction is equal to the sum of the heats of reaction for the individual reactions.

Step 1: Equation 1: 2 KOH + H2SO4 → K2SO4 + 2 H2O
The heat of reaction for this equation is -27.2 kcal/mol.

Step 2: Equation 2: Mg(OH)2 + H2SO4 → MgSO4 + 2 H2O
The heat of reaction for this equation is also -27.2 kcal/mol.

Step 3: Equation 3: 3 Ca(OH)2 + 2 H3PO4 → Ca3(PO4)2 + 6 H2O
To find the heat of reaction for this equation, we can use Hess's Law.

Step 4: We can rewrite equation 3 as the sum of equations 1 and 2:
3 Ca(OH)2 + 2 H3PO4 → Ca3(PO4)2 + 6 H2O
= 3(2 KOH + H2SO4) + 2( Mg(OH)2 + H2SO4) → Ca3(PO4)2 + 6 H2O

Step 5: Applying Hess's Law, the heat of reaction for equation 3 is the sum of the heats of reaction for equations 1 and 2:
Heat of reaction for equation 3 = 3(Heat of reaction for equation 1) + 2(Heat of reaction for equation 2)
= 3(-27.2 kcal/mol) + 2(-27.2 kcal/mol)
= -81.6 kcal/mol

Answer:
The heat of reaction for the reaction 3 Ca(OH)2 + 2 H3PO4 → Ca3(PO4)2 + 6 H2O is -81.6 kcal/mol. Therefore, option (C) -81.6 kcal/mol is the correct answer.
Community Answer
The heat of reaction of both the reactions 2 KOH H2SO4 → K2SO4 2H2...
Option C.....-81.6kcal/mol.
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The heat of reaction of both the reactions 2 KOH H2SO4 → K2SO4 2H20 and Mg(OH)2 H2SO4 → MgSO4 2 H2O is -27.2 kcal/mol. Hence the heat of reaction of 3 Ca(OH)2 2 H3PO4 → Ca3(PO4)2 6 H2O would be (A)-13.6 kcal/mol (B)-27.2 kcal/mol (C)-81.6 kcal/mol (D) -68.0 kcal/mol​?
Question Description
The heat of reaction of both the reactions 2 KOH H2SO4 → K2SO4 2H20 and Mg(OH)2 H2SO4 → MgSO4 2 H2O is -27.2 kcal/mol. Hence the heat of reaction of 3 Ca(OH)2 2 H3PO4 → Ca3(PO4)2 6 H2O would be (A)-13.6 kcal/mol (B)-27.2 kcal/mol (C)-81.6 kcal/mol (D) -68.0 kcal/mol​? for IIT JAM 2024 is part of IIT JAM preparation. The Question and answers have been prepared according to the IIT JAM exam syllabus. Information about The heat of reaction of both the reactions 2 KOH H2SO4 → K2SO4 2H20 and Mg(OH)2 H2SO4 → MgSO4 2 H2O is -27.2 kcal/mol. Hence the heat of reaction of 3 Ca(OH)2 2 H3PO4 → Ca3(PO4)2 6 H2O would be (A)-13.6 kcal/mol (B)-27.2 kcal/mol (C)-81.6 kcal/mol (D) -68.0 kcal/mol​? covers all topics & solutions for IIT JAM 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for The heat of reaction of both the reactions 2 KOH H2SO4 → K2SO4 2H20 and Mg(OH)2 H2SO4 → MgSO4 2 H2O is -27.2 kcal/mol. Hence the heat of reaction of 3 Ca(OH)2 2 H3PO4 → Ca3(PO4)2 6 H2O would be (A)-13.6 kcal/mol (B)-27.2 kcal/mol (C)-81.6 kcal/mol (D) -68.0 kcal/mol​?.
Solutions for The heat of reaction of both the reactions 2 KOH H2SO4 → K2SO4 2H20 and Mg(OH)2 H2SO4 → MgSO4 2 H2O is -27.2 kcal/mol. Hence the heat of reaction of 3 Ca(OH)2 2 H3PO4 → Ca3(PO4)2 6 H2O would be (A)-13.6 kcal/mol (B)-27.2 kcal/mol (C)-81.6 kcal/mol (D) -68.0 kcal/mol​? in English & in Hindi are available as part of our courses for IIT JAM. Download more important topics, notes, lectures and mock test series for IIT JAM Exam by signing up for free.
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