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Osmotic pressure method is the most accurate and reliable method among the 4 colligative properties based molecular mass measurement methods. Due to inverse relationship between the molar mass of solute and the measured colligative property, the highest difficulty is observed for the measurement of molar mass of high molecular weight species like polymers, ...


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Your question is about the measurement of carbon-13 mass. After long efforts of physicists and chemists (more than two centuries), it was decided that everyone will measure the atomic mass with respect to carbon-12, defined exactly as 12 g/mol. Once this value was set, every element was measured relative to this particular carbon isotope. Before mass ...


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The main issue is that the structures that are named 1° carbocation and 2° carbocation in the question are not different structures. As a general rule in mass spectrometry, ionization is postulated to occur from the highest occupied molecular orbital, which is usually for alkenes the $\pi$ orbital. Removing an electron from a $\pi$ orbital leads to a singly ...


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The suggested formation of the allyl cation is not a contradiction of the Stevenson rule. «What is the statement of Stevenson’s rule? When a fragmentation takes place, the positive charge remains on the fragment with the lowest ionization energy.» Jürgen H. Gross, public answer key for question 6.1c) on his companion site to Mass spectroscopy, 3rd edition (...


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