C2.3 Atomic structure, analysis, and quantitive chemistry

Question 1

What is the mass number in this atom:

23
Na
11

Answer 1

The top number: 23

Question 2

What is the atomic number in this atom:

23
Na
11

Answer 2

The bottom number: 11

Question 3

What is the relative mass of a proton?

Answer 3

1

Question 4

What is the relative mass on a neutron?

Answer 4

1

Question 5

What is the relative mass on an electron?

Answer 5

Very small

Question 6

What is the mass number?

Answer 6

The total number of protons and neutrons in an atom

Question 7

What is the name for atoms of the same element can have different numbers of neutrons?

Answer 7

Isotopes of that element

Question 8

What does the relative atomic mass of an element compare the mass of atoms of the element with?

Answer 8

The Carbon 12 isotope. it is an average value for the isotopes of the element

Question 9

What is the relative formula mass of a compound?

Answer 9

The sum of the relative atomic masses of the atoms in the numbers shown in the formula

Question 10

The is the relative formula mass of a substance, in grams, known as?

Answer 10

One mole of that substance

Question 11

What is the relative atomic mass of an element?

Answer 11

The mass number of an element

Question 12

How can elements and compounds be detected?

Answer 12

Using instrumental methods

Question 13

What are instrumental methods often?

Answer 13

Accurate, sensitive, rapid and are particularly useful when the amount of a sample is very small

Question 14

How can artificial colours be detected and identified in foods?

Answer 14

Paper chromatography

Question 15

What should be used to draw the baseline on filter paper and why?

Answer 15

A pencil because pen ink would run with the water

Question 16

What are examples of instrumental methods?

Answer 16

Gas chromatography and mass spectroscopy

Question 17

What does gas chromatography allow?

Answer 17

The separation of a mixture of different compounds

Question 18

What can the time taken for a substance to travel through the column be used for?

Answer 18

Identifying the substance

Question 19

What happens in a gas chromatography column?

Answer 19

Different substances, carried by gas, travel through a column packed with solid material at different speeds so that they become separated

Question 20

What do the different peaks on a gas chromatograph show?

Answer 20

The number of compounds present

Question 21

What do the position of the peak on a gas chromatograph show?

Answer 21

The retention time

Question 22

What can a mass spectrometer do?

Answer 22

Identify substances vert quickly and accurately and can detect very small quantities

Question 23

What is the molecular mass given by?

Answer 23

The molecular ion peak

Question 24

What can the mass spectrometer also give us?

Answer 24

The relative molecular mass of each of the substances separated in the column

Question 25

What is the retention time?

Answer 25

The time taken to reach the detector

Question 26

How can the percentage of an element in a compounds be calculated?

Answer 26

Relative atomic mass x number of atoms in that element divided by / The relative formula mass of the entire compound times by x 100

Question 27

What is the first step for calculating the empirical formula?

Answer 27

List all the elements in the compound

Question 28

What is the second step for calculating the empirical formula?

Answer 28

Underneath, write their masses or percentages given to you

Question 29

What is the third step for calculating the empirical formula?

Answer 29

Divide each mass or percentage by the relative atomic mass for that particular element

Question 30

What is the fourth step for calculating the empirical formula?

Answer 30

Turn the numbers into a nice and simple ratio by multiplying/dividing by a nice number like 10

Question 31

What is the fifth step for calculating the empirical formula?

Answer 31

Get the ration into its simplest form, this then tells you which numbers should follow each element giving you the empirical formula

Question 32

What is the first step in calculating the masses of reactants and products from a reaction?

Answer 32

Write out the balanced symbol equation

Question 33

What is the second step in calculating the masses of reactants and products from a reaction?

Answer 33

Work out the relative formula mass for the two bits you need

Question 34

What is the third step in calculating the masses of reactants and products from a reaction?

Answer 34

Apply the rule divide to get one, then multiply to get all

Question 35

Why is it not possible to obtain the calculated amount exactly?

Answer 35

Although no atoms are gained or lost, it is possible not to gain the full amount because: the reaction may be reversible, some product may be lost when removed from the reaction mixture (e.g. filtering) and sometimes other reactions occur which use up the reactants

Question 36

How do you calculate the percentage yield?

Answer 36

``` actual yield (grams) / x 100 predicted yield (grams) ```

Question 37

What is a reversible reaction?

Answer 37

One where the products of the reaction can themselves react to produce the original reactants

Question 38

How can reversible reactions be represented?

Answer 38

With an arrow