Answer:
The heat of reaction when hydrogen and oxygen combine to form water is :
<u>C. 571.6 kJ</u>
Explanation:
Enthalpy Change = The enthalpy change for the formation of 1 mole of the substance from their standard state is called the enthalpy of formation.
This is intensive quantity as it is fixed for 1 mole .
Intensive properties = Those properties which are independent on the amount of the substance are intensive properties.
The value of these quantities does not get halve if you divide the substance into two equal parts. example , density, refractive index.
However , the enthalpy of reaction is extensive. Because on increasing the amount the value of the enthalpy also get doubles
Hence for this reaction :
Its value is -285.8 kJ for 1 mole
And here two moles are present . so the value of molar enthalpy is:
-285.8 x 2 = -571.6 kJ
In chemistry, the molar mass M is a physical property defined as the mass of a given substance (chemical element or chemical compound) divided by its amount of substance. The base SI unit for molar mass is kg/mol. However, for historical reasons, molar masses are almost always expressed in g/mol.
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~Emmy <3
Answer: 121.7558 amu
Explanation:
Average atomic mass of the unknown element =
(Mass of isotope 1 x Relative Abundance of Isotope 1) + ( Mass of Isotope 2 x Relative Abundance of Isotope 2)
(120.9 x 0.5721) + (122.9 x 0.4279) = 69.16689 + 52.58891
Average mass of the unknown element = 121.7558 amu
This reaction obeys the law of conservation of mass.
Explanation:
In the burning reaction, methane (CH₄) react with oxygen (O₂) to produce carbon dioxide (CO₂) and water (H₂O):
CH₄ + 2 O₂ → CO₂ + 2 H₂O
Now we calculate the number of moles of methane and carbon dioxide:
number of moles = mass / molar weight
number of moles of methane = 10 / 16.04 = 0.62 moles
number of moles of carbon dioxide = 27 / 44.01 = 0.61 moles
From the chemical reaction we see that 1 mole of methane produces 1 moles of carbon dioxide so 0.6 moles of methane produces 0.6 mole of carbon dioxide. This reaction obeys the law of conservation of mass because the mass of reactants is equal to the mass of products.
Learn more about:
combustion reaction
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