# Relative Mass Terms

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• Created by: zoolouise
• Created on: 04-04-16 11:01
What is the definition of relative atomic mass?
Relative atomic mass is the average mass of one atom of the element 1/12 the mass of one atom of carbon-12
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What is the definition of relative isotopic mass?
Relative isotopic mass is the mass of an atom of an isotope relative to 1/12 the mass of an atom of carbon-12
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What is the definition of relative formula mass?
Relative formula mass is the average mass of a molecule relative to 1/12 the mass of an atom of carbon-12
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What does the mass of an element depend on?
The mass of an element depends on the relative abundance of all the isotopes present in the sample.
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What do chemists use?
They use an average mass of all the atoms and call it relative atomic mass, Ar. It has no units as it's one mass compared with another mass.
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What do we use is we refer to the mass of a particular isotope?
If we refer to the mass of a particular isotope then the term relative isotopic mass is used.
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What does the formula of a compound show?
It shows the ratio that the atoms combine in.
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How do you work out the mass of a compound?
In order to find the mass of a compound, add each of the Ar's together and this will give you the Mr, the relative formula mass.
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What two things does the mass spectrometer measure?
The mass of each different isotope of the element and the relative abundance of each isotope of an element
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What are the four steps within the mass spectrometer?
Ionisation Acceleration Deflection Detection
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What is ionisation?
Ionisation is where the gaseous sample is bombared with high-energy electrons which ionises the sample as some electrons are lost, this makes a positive ion.
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What is acceleration?
Acceleration is where the electric field accelerates the positive ions to a high speed towards the negative plate, it then enters a magnetic field
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What is deflection?
Deflection is where the different ions are deflected according to their mass and charge of the ion
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What is detection?
Detection is the beam of ions passing through the machine is electrically detected. Ions with the correct mass/charge ratio make it through the machine to the ion detector. The signals amplified and recorded, the process results in a mass spectrum.
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What is the relative atomic mass?
The relative atomic mass is a weighted average of masses of all the atoms in the isotopic mixture.
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What are the three other uses of the mass spectrometry?
Identify unknown compounds, Identifying trace compounds in forensic science, Analysing molecules in space
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## Other cards in this set

### Card 2

#### Front

What is the definition of relative isotopic mass?

#### Back

Relative isotopic mass is the mass of an atom of an isotope relative to 1/12 the mass of an atom of carbon-12

### Card 3

#### Front

What is the definition of relative formula mass?

### Card 4

#### Front

What does the mass of an element depend on?

### Card 5

#### Front

What do chemists use?