Answer:
Atom
Explanation:
The smallest unit which maintains an element's properties is an atom.
The chemical reaction of Cavendish involving zinc would be a reaction between hydrochloric acid and zinc yielding zinc chloride and hydrogen gas. The balanced chemical equation would be:
2Zn + 2HCl = 2ZnCl + H2
This is an example of a single replacement reaction where zinc replaces hydrogen in the acid molecule.
The enthalpy of reaction for the combustion of ethane 2CH₃CH₃ + 7O₂ → 4CO₂ + 6H₂O calculated from the average bond energies of the compounds is -2860 kJ/mol.
The reaction is:
2CH₃CH₃ + 7O₂ → 4CO₂ + 6H₂O (1)
The enthalpy of reaction (1) is given by:
(2)
Where:
r: is for reactants
p: is for products
The bonds of the compounds of reaction (1) are:
- 2CH₃CH₃: 2 moles of 6 C-H bonds + 2 moles of 1 C-C bond
- 7O₂: 7 moles of 1 O=O bond
- 4CO₂: 4 moles of 2 C=O bonds
- 6H₂O: 6 moles of 2 H-O bonds
Hence, the enthalpy of reaction (1) is (eq 2):
Therefore, the enthalpy of reaction for the combustion of ethane is -2860 kJ/mol.
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