A.) In the beginning the universe was too hot for atoms to exist.
Because choice b,c,and d are all part of the big bang theory.
The mass of NaCl sample has been 24.3 g. Thus, option A is correct.
The heat of fusion has been the amount of heat required to convert 1 mole of substance into solid to liquid state.
The heat required has been given as:

<h3>Computation for the mass of NaCl</h3>
The given solution has heat of fusion, 
The heat required to melt the sample has been, 
Substituting the values for the mass of NaCl

The mass of NaCl sample has been 24.3 g. Thus, option A is correct.
Learn more about heat of fusion, here:
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Silver/Electron configuration
[Kr] 4d¹⁰ 5s¹
Atomic number: 47
Symbol: Ag
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Answer: 1. 2.7 moles of ammonia are formed
2. 12.0 moles of hydrogen are required
3. 2.0 moles of nitrogen are required
Explanation:
The balanced chemical equation is:

According to stoichiometry:
3 moles of hydrogen form = 2 moles of ammonia
Thus 4.0 moles of hydrogen form =
of ammonia
According to stoichiometry:
2 moles of ammonia are formed by = 3 moles of hydrogen
Thus 8.0 moles of ammonia are formed by =
of hydrogen
According to stoichiometry:
3 moles of hydrogen react with = 1 mole of nitrogen
Thus 6.0 moles of hydrogen react with =
of nitrogen
A model of the atom devised by Ernest Rutherford.