Relative Mass Flashcards

1
Q

What is the standard isotope for relative mass?

A

Carbon-12

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2
Q

What are the units for atomic mass units?

A

u

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3
Q

How many atomic mass units are in a carbon-12 isotope?

A

12u

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4
Q

What is the standard mass for atomic mass?

A

1u

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5
Q

What is 1u equivalent to?

A

1/12 of an atom of carbon-12

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6
Q

What is 1u approximately the mass of?

A

A proton or neutron.

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7
Q

What is the 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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8
Q

What are the units for relative isotopic mass?

A

There are no units because it is a ratio between two masses.

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9
Q

What is the relative atomic mass?

A

This is 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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10
Q

What is the abbreviation for relative atomic mass?

A

Ar

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11
Q

What does the weighed mean mass take into account?

A

The percentage abundance of each isotope.

The relative isotopic mass of each isotope.

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12
Q

What is used to find the % abundance of the isotopes in a sample of an element?

A

A mass spectrometer.

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13
Q

What does this mean: m/z?

A

This is the mass-to-charge ratio

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14
Q

How do you find m/z?

A

relative mass of ion/relative charge on ion

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15
Q

What happens to a sample in a mass spectrometer?

A

The sample is vaporised and then ionised.

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16
Q

What type of ions are formed in a mass spectrometer?

A

Positive ions.

17
Q

What happens to the ions in the mass spectrometer?

A

They are accelerated.

18
Q

What part of each isotope is separated?

A

The ions.

19
Q

Why are the ions separated?

A

Heavier ions are harder to deflect than lighter ions.

20
Q

How do you find the relative atomic mass of a sample?

A

(isotope mass number*%abundance)+(same again for next isotope)/100

21
Q

What is the difference between ionic and covalent bonding?

A

In ionic bonding electrons are transferred.

In covalent bonding electrons are shared.

22
Q

What does a displayed formula of a covalent.y bonded molecule show?

A

The relative position of atoms and the bonds between them as lines.

23
Q

What are lone pairs?

A

Paired electrons that are not shared.

24
Q

How are lone pairs shown in displayed formulas?

A

They are shown as dots (..).

25
Q

Which molecule shows that predictions for bonding cannot be based solely on the noble gas electron structure?

A

BF3

26
Q

What is mean by expansion of the octet?

A

When there are more electrons in the outer shell than in the nearest noble gas.

27
Q

From which shell is expansion of the octet from?

A

N=3