Answer: 780 kcal are required to produce 12.00 mol of 
Explanation:
Endothermic reactions are defined as the reactions in which energy of the product is greater than the energy of the reactants. The total energy is absorbed in the form of heat and written along with reactants.
The balanced chemical reaction is:
According to stoichiometry :
2 moles of
are produced by absorption of energy = 130 kcal
Thus 12.00 moles of
are produced by absorption of energy = 
Thus 780 kcal are required to produce 12.00 mol of 
This problem is providing the mass of both magnesium metal and oxygen gas and involved in a chemical reaction and asks for the limiting reactant. At the end, it turns out to be identified as magnesium.
<h3>Stoichiometry</h3>
In chemistry, stoichiometry is a widely-used tool we use in order to relate the mass and moles of different chemical substances involved in a chemical reaction. Thus, we consider the following chemical equation between magnesium and oxygen to produce magnesium oxide.

However, when the mass of the both of the reactants is given, one must identify the limiting reactant as the one producing the least of the moles of the product, which means we can use the given grams of the both of the reactants, their molar masses and mole ratios with the product to obtain the aforementioned:

Thus, we can evidence how 24 g of magnesium produce the least of the moles of magnesium oxide, fact validating the magnesium as the limiting reactant and the oxygen as the excess one.
Learn more about stoichiometry: brainly.com/question/9743981
he mass defect of the helium nucleus ⁴He₂ is 0.030377 u
Further explanation
Mass defect means the difference between the mass of particles forming an atom with an atomic mass.
Δm = mass defect ( u )
mp = mass of proton ( u )
me = mass of electron ( u )
mn = mass of neutron ( u )
M = atomic mass ( u )
A = mass number
Z = atomic number
Let us now tackle the problem !
Given :
Unknown :
Δm = ?
Solution :
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Answer details
Grade: College
Subject: Physics
Chapter: Nuclear Physics
Keywords: Mass , Defect , Nucleon , Number , Atomic , Proton , Electron , Neutron
Explanation:
A.
The first student will be on the lower bunk on the first floor because 1. They want on the lowest available floor and 2. They want to be in a lower bunk if available.
B.
7 students are in the TOP bunks because 1. They want on the lowest available floor and 2. They want to be in a lower bunk if available. Therefore, all the rooms up till the third floor (Remember, third floor has 3 suites), so the first floor is filled - 1 person on the top bunk, 2 floor is filled- 4 persons and the third floor; the first suite is filled - 1 person and the second suite is a little partially filled- 1 person.
C.
Following the criteria 1, 2 and 3, the 21st student occupies the third suite on the third floor because all the floors (1 and 2) are occupied so the third suite on the third floor is still vacant.
D.
From the criteria there are therefore 10 persons at the TOP bunk. All the rooms up till the third floor are filled, so the first floor is filled - 1 person on the top bunk, second floor is filled (2 suites) - 4 persons and the third floor; the first suite and second suite is filled - 4 persons; the thirs suite has 6 persons present so 1 person is at the top bunk.
Answer:
true
because with the both states we increase the surface of reaction