Chem 1a Flashcards

1
Q

Other than relative mass of each isotope, what else would need to be known for the Ar of Cr to be calculated?

A

Need relative abundance of each element

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2
Q

Why must the sample be ionised in a TofF spectrometer?

A

So it can be accelerated and can be pick up an electron at the detector.

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3
Q

In TofF, what needs to be adjusted to allow distinction between samples of different isotopes?

A

Magnetic field

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4
Q

Explain how the adjustment of magnetic field in TofF enables isotopes of the sample to be separated?

A

Deflection depends on mass or m/z

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5
Q

Why does Neon have a high first IE than Na?

A

Electron is being removed from a shell of lower energy, e– is removed from 2p rather than from 3s, less shielding

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6
Q

1st ionisation energy

A

Enthalpy change when an electron is removed from 1 mole of gaseous atoms.

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7
Q

Why is a mass spectrometer incapable of distinguishing between the ions 14N+ and 14N(2+)2?

A

same M/Z

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8
Q

Why would F- be unlikely to reach the detector?

A

Not accelerated

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9
Q

Why does He has a higher first ionisation energy than Li?

A

He’s e- in 1s, so closer to nucleus and no shielding.

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10
Q

Explain why beryllium has a higher first ionisation energy than boron

A

Be’s outer electron in 2s, which is lower in energy than 2p

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11
Q

Explain why the first ionisation energy of krypton is greater than the first ionisation energy of bromine.

A

Greater nuclear charge, and similar shielding throughout atom.

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12
Q

Explain why the second ionisation energy of beryllium is greater than the first ionisation energy.

A

E- being removed from positive ion, so greater attraction present.

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13
Q

Why does water not affect titre value?

A

Water does not change the number of moles of either reagent

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14
Q

Suggest ways to improve a titration?

A
  • Wash solid from weighing container into the beaker
  • Wash rod after use
  • Wash beaker after transfer to flask
  • Wash filter funnel after transfer
  • Use teat pipette to make up to the mark on flask
  • Ensure bottom of meniscus is on graduation mark
  • Mix final solution in flask
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15
Q

How is TOF able to separate isotopes in a sample?

A

Cations are accelerated to a constant kinetic energy, different m/z have the same kinetic energy and move faster, ions with lower m/z arrive first at the detector.

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