# Calculations

All the calculations with examples

Teacher recommended

- Created by: Georgia 753
- Created on: 11-04-16 13:19

First 205 words of the document:

Calculations

~ Unit 1 and Unit 2 ~

Mass Spectrometry Calculation

(Abundance1x m/z + (Abundance

1) 2x m/z + (Abundance

2) 3x m/z3)

Total Abundance

Example 1

Find the relative atomic mass of iron using the following data:

54 56 57 58

Fe (5.8%) Fe (91.6%) Fe (2.2%) Fe (0.3%)

Ar =((54 x 5.8) + (56 x 91.6) + (57 x 2.2) + (58 x 0.3))

(5.8 + 91.6 + 2.2 + 0.3)

= 55.91 56

Example 2

A sample of sulphur consisting of three isotopes has a relative atomic mass of32.16 . The following data gives

information about the relative abundance of two of the isotopes:

32 33

S (91.0%) S (1.8%)

Use this information to find the relative abundance and hence the mass of the third isotope

32.16 = ((32 * 91) + (33 * 1.8) + (x * (100-91-1.8)))

100

3216 = 2971.4 + 7.2x

7.2x= 244.6

x= 244.6

7.2

= 33.97 34

Mass Number and Relative Atomic Mass

The mass number is the top number of an element in the periodic table. This can be used to calculate the number of

neutrons. The bottom number situated on an element is the relative atomic mass and is also known as the proton

number.

Example

Calculate the number of protons, electrons and neutrons in 15 6C

Relative atomic mass = No. of protons = No. of electrons = 6

Neutrons = mass atomic mass = 15 6 = 9

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