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What are the three pieces of evidence that disprove the Kekulé model of Benzene?

The enthalpy change of hydrogenation is less exothermic than suggested by the Kekulé model ( -208kJmol -1 instead of the expected -357kJmol -1 ), meaning Benzene is more thermodynamically stable than the Kek...
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There are two stable isotopes of Bromine, Br-79, Br-81. If a sample of Br2 is fed into a mass spectrometer, how many peaks would be observed in the spectrum?

There should be five peaks. In the process of bombarding the Br2 molecule with electrons to charge it, the molecule can fragment into 2 Br atoms. We should therefore expect to see peaks at 79 and 81 m/z. The...
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Answered by Tim H. • Chemistry tutor
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Calculate the pH of a 0.025 mol dm-​3​ solution of methanoic acid. For HCOOH, Ka = 1.58 x 10-​4​ mol dm-​3

This question is an acid calculation question so it requires you to recall key formulas relating to weak acids. As the Ka of HCOOH has been given, I would start by writing an expression for Ka. Ka= [HCOO-​ ]...
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Answered by Radia H. • Chemistry tutor
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How does Hydrogen bonding arise in Water?

Hydrogen bonding occurs in water due to the large electronegativity difference between the hydrogen atoms and the oxygen atom.The oxygen attracts the shared pair of electrons towards itself leaving the hydro...
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How do you calculate lattice enthaply?

You can't directly measure lattice enthalpy of a solid crystal, so you have to look at a different method. Usually this would be experimentally or using Hess's Law to construct a Born-Haber cycle. The Born-H...
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