2.2 Relative Mass Flashcards

1
Q

The strong nuclear force holding together protons and neutrons comes at the expense of the loss of…

A

…a fraction of their mass (the mass defect)

This was found out by Albert Einstein

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2
Q

What is the standard isotope to base all atomic masses on

A

Carbon-12 isotope

One atom has a mass of approx. 1.99*10^-26kg

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3
Q

What is the unit of atomic mass

A

u

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4
Q

What is the mass of a carbon-12 isotope

A

12u

Ie. Exactly 12 atomic mass units

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5
Q

1u is approximately the mass of…

A

…a proton or a neutron

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6
Q

What is relative isotopic mass

A

The mass of an isotope relative to 1/12th of the mass of an atom of carbon-12

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7
Q

What is relative atomic mass

A

The weighted mean mass of an atom of an element relative to 1/12th of the mass of an atom of carbon- 12

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8
Q

What is the symbol for relative atomic mass

A

Ar

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9
Q

The weighted mean mass takes account of…

A

…the percentage abundance of each isotope and the relative isotopic mass of each isotope

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10
Q

How can we determine the relative atomic mass

A

Use a mass spectrometer

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11
Q

How do mass spectrometers work

A

1) A sample is placed in the mass spectrometer
2) The sample is vaporised and then ionised to form positive ions
3) The ions are accelerated. Heavier ions move more slowly and are more difficult to deflect than lighter ions, so the ions of each isotope are separated.
4) The ions are detected on a mass spectrum as a mass-to-charge ratio m/z. Each ion reaching the detector adds to the signal so the greater the abundance, the larger the signal

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12
Q

How to find the mass to charge ratio

m/z

A

Relative mass of ion/relative charge on ion

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13
Q

For an ion with one positive charge, the m/z ratio is equivalent to…

A

…the relative isotopic mass which is recorded on the x ais of the spectrum

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14
Q

How to find the relative atomic mass from the mass numbers of each isotope

A

Relative atomic mass=(%isotope number)+(%isotope number) / 100

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15
Q

How to determine the relative isotopic mass

A

Using a mass spectrometer to record the accurate m/z ratio

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