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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The mass of one mole of water it is 18 amu, but you need to find the mass of a molecule of water, therefore you calculate the mass of one mole of water, which is 18 amu and you divided by Avogadro's number which is 6,022 x 10^23. The result is 2,989 x 10^-23. Hope I helped you. If you have any questions ask :) Good luck.
Four people weigh a standard mass of 10.00 g on the same balance. The set of readings suggest measurements that are neither precise <span>nor accurate is the one with less mass</span>
Answer:
Enthalpy of formation = -947.68KJ/mol
Explanation:
Enthalpy of formation is the heat change when one mole of a substance is formed from its element in its standard states and in standard conditions of temperature and pressure. it may be positive or negative, if positive, it is an endothermic reaction where the heat content of the product is greater than that of the reactants, and if negative, it is exothermic reaction - where the heat content of the reactants is greater than the products. the enthalpy of formation is measured in KiloJoule/Moles (KJ/Mole).
From the value of the enthalpy of formation of NaHCO3, it shows that the reaction is exothermic, that is the formation of NaHCO3 from its constituents elements. As such, the heat content of the reactants is greater than the products.
The step by step explanation is shown in the attachment.
Metalloids are metallic-looking brittle solids<span> that are either semiconductors or exist in semiconducting forms, and have amphoteric or weakly acidic oxides. Typical </span>nonmetals<span> have a </span>dull<span>, coloured or colourless </span>appearance<span>; are </span>brittle<span> when </span>solid<span>; are poor conductors of heat and electricity; and have acidic oxides.</span>