Answer:
= 100kJ
Explanation:
The reverse reaction's activation energy of a reaction is the activation energy of the forward reaction plus ΔH of the reaction:
Ea of forward reaction =75kJ
∆H = -175 kJ/mol
Ea of reverse reaction = 75 +(-175)
= 100kJ
Note that a reverse reaction is one which can proceed in both direction depending on the conditions.
Im pretty sure it's element
Explanation:
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Answer:
A. there is an isotope of lanthanum with an atomic mass of 138.9
Explanation:
By knowing the different atomic masses of both Lanthanum atoms, we can not tell anything about their occurence in nature. Therefore, all the last three options are incorrect. Because, the atomic mass does not tell anything about the availability or natural abundance of an element.
Now, the isotopes of an element are those elements, which have same number of electrons and protons as the original element, but different number of neutrons. Therefore, they have same atomic number but, different atomic weight or atomic masses.
Hence, by looking at an elements having same atomic number, but different atomic masses, we can identify them as isotopes.
Thus, the correct option is:
<u>A. there is an isotope of lanthanum with an atomic mass of 138.9.</u>
Neon I think. Go to the periodic table and see which one is the 11th
