In which one of the following processes will the ΔHf have the opposite sign to that of the other three?
A - VCE - SSCE Chemistry - Question 13 - 2005 - Paper 1
Question 13
In which one of the following processes will the ΔHf have the opposite sign to that of the other three?
A. l(s) → l(g)
B. Na(g) + e⁻(g) → Na(g)
C. CO₂(g) → C(s... show full transcript
Worked Solution & Example Answer:In which one of the following processes will the ΔHf have the opposite sign to that of the other three?
A - VCE - SSCE Chemistry - Question 13 - 2005 - Paper 1
Step 1
A. l(s) → l(g)
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Answer
This process represents the melting of a solid to a liquid, which is an endothermic process. Its ΔHf is positive.
Step 2
B. Na(g) + e⁻(g) → Na(g)
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Answer
This reaction represents the ionization of sodium, which is an exothermic process as energy is released when an electron is gained. Its ΔHf is negative.
Step 3
C. CO₂(g) → C(s) + O₂(g)
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Answer
This reaction indicates the decomposition of carbon dioxide into carbon and oxygen, which generally requires energy, making it endothermic. Thus, its ΔHf is positive.
Step 4
D. 2NaCl(s) → 2Na(l) + Cl₂(g)
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Answer
The decomposition of sodium chloride into liquid sodium and chlorine gas is also an endothermic process, leading to a positive ΔHf.
