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Answer:
The u (amu is the old unit name) is 1/12 of the weight of an 12C atom. The way the u is chosen ensures that all core and atom masses are multiples of 1(±0.1) u.
Explanation:
Further explanation if needed...
Carbon 12 was chosen because the chemical atomic weights based on C12 are almost identical to the chemical atomic weights based on the natural mix of oxygen. Simply because the atomic mass is defined as 1/12 of the mass of 12C. Others isotopes of carbon (13C mostly, with an abundance of 1.1% approximately) account for an average atomic mass slightly above 12.
White phosphorus burns spontaneously in chlorine to produce a mixture of two chlorides, phosphorus (ii) chloride and phosphorus(v) chloride and heat is evolved. Phosphorus (iii) chloride is a colorless fuming liquid:
P4 + 6Cl2 = 4PCl3
Phosphorus (v) chloride is an off-white solid
P4 +10Cl2 = 4PCl5
The answer is 207.2 grams.
