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***2013 LC Chemistry Before/After***
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Acciaccatura wrote: »Quiz time again!
1. What is dative covalent bonding?A bond formed where the two shared electrons come from one atom, e.g. in the hydronium ion H3O+
2. What is the difference between heat of combustion and heat of reaction?Heat of reaction is measured in KJ, heat of combustion is measured in KJ/mol
3. Name the product formed when ethanol reacts with sodium.sodium ethoxide
4. Give an example of a reaction with an autocatalyst.Reaction of KMnO4 with Fe2+ and dilute H2SO4, autocatalyst is Mn2+
5. Why does the pH of pure water change at different temperatures?pH is measured at 25 degrees Celsius, does not give true reading outside these values
6. What is the catalyst used in the Haber process?Iron (Fe)
7. In equilibrium calculations, when does the volume of the container not matter?When there are the same number of moles of gas on either side of the equation
8. What unit is ionisation energy measured in?KJ/mol
9. In KMnO4 titrations, (i) why do you need to add sulphuric acid? (ii) What do you observe when you don't?(i) Brown colour due to MnO2 (ii) without the acid KMnO4 does not work at full oxidising power
10. Why do aldehydes and ketones have higher boiling points than corresponding alkanes?There are dipole-dipole forces present in aldehydes and ketones not present in alkanes
11. Give an example of a flocculating agent.Aluminium sulphate
This one has me snookered. Can anyone explain? 12. Why is ethanal more soluble in water than its corresponding alkane ethane?
Are you sure about the answer to question 2? I thought all "heats of" are Kj/mol0 -
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Why does each element have a unique emission spectrum, other than because they all have unique electronic configurations?
This is most definitely a question to test all of your knowledge, it is in no way me trying to exploit you all for your knowledge. Of course not.
Hmm so when elements become "excited" electrons move from lower energy levels to higher ones. They are very unstable here and fall back to their positions. They emit definite energy when they fall back and each element has a different amount of energy released
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MarieCurie22 wrote: »Unique number of shells, different samples (ie some contain more atoms...less energy absorbed by each)
Different sub levels (although that essentially the same as the electronic config....hmmm....each atoms absorb different frequencies of light?
All samples contain the same number of atoms (avogadro number) The only thing that changes to give the Balmer series is, the normal emitting a photon/packet of energy as it transitions from one state to another. Although the movement is basically the same, the energy for each transition is different depending on the attractive forces between the electron and the nucleus, hence the different lines in the series
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All samples contain the same number of atoms (avogadro number) The only thing that changes to give the Balmer series is, the normal emitting a photon/packet of energy as it transitions from one state to another. Although the movement is basically the same, the energy for each transition is different depending on the attractive forces between the electron and the nucleus, hence the different lines in the series
No all samples dont contain the same number of atoms....all moles contain the same number not samples!0 -
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