Answer: c. 179 kJ/mol
Explanation:
According to Hess’s law of constant heat summation, the heat absorbed or evolved in a given chemical equation is the same whether the process occurs in one step or several steps.
According to Hess’s law, the chemical equation can be treated as algebraic expressions and can be added or subtracted to yield the required equation. That means the enthalpy change of the overall reaction is the sum of the enthalpy changes of the intermediate reactions.
Given:
(1)
(2)
(3)
(4)
On subtracting eq (1) from eq (2) we have:
-
Hence the enthalpy change for the raection is 179.0 kJ/mol.
Answer:
When a Magnesium Ribbon is burnt, a powdery substance called magnesium oxide is formed.
Explanation:
There has obviously been a chemical change because several chemical properties of the magnesium have been modified: the color, the texture and the mass.
The increase in mass is due to the fact that oxygen from the air has combined with the magnesium to make magnesium oxide, MgO.
The chemical equation, Mg + O2 MgO shows this reaction but it needs to be balanced to make 2Mg + O2 2MgO.
Using stoichiometry, we can convert this eqation into an equation with moles:
2 mol Mg + 1 mol O2 2 mol MgO.
Next, we convert to grams using atomic masses obtained from the periodic table:
48g Mg + 32g O2 80g MgO
Lastly, we determine the same thing in the proportions we used. In other words, we used only 0.15g of Mg (not 48g) so everything needs to be divided by 320. So 80 / 320 = 0.25 g. If we burn 0.15 g of Mg, we obtain 0.25 g of MgO.
Hope this helps!!!
This is my first answer.
The correct answer is C - sound.
Sound is a wave, and it is thus not considered a form of matter.
Answer:chlorofluorocarbons (CFCs)
halon.
carbon tetrachloride (CCl4)
methyl chloroform (CH3CCl3)
hydrobromofluorocarbons (HBFCs)
hydrochlorofluorocarbons (HCFCs)
methyl bromide (CH3Br)
bromochloromethane (CH2BrCl)
Explanation:
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