C2.3 Atomic structure, analysis, and quantitive chemistry Flashcards Preview

Chemistry: C2 > C2.3 Atomic structure, analysis, and quantitive chemistry > Flashcards

Flashcards in C2.3 Atomic structure, analysis, and quantitive chemistry Deck (38)
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1
Q

What is the mass number in this atom:

23
Na
11

A

The top number: 23

2
Q

What is the atomic number in this atom:

23
Na
11

A

The bottom number: 11

3
Q

What is the relative mass of a proton?

A

1

4
Q

What is the relative mass on a neutron?

A

1

5
Q

What is the relative mass on an electron?

A

Very small

6
Q

What is the mass number?

A

The total number of protons and neutrons in an atom

7
Q

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

A

Isotopes of that element

8
Q

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

A

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

9
Q

What is the relative formula mass of a compound?

A

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

10
Q

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

A

One mole of that substance

11
Q

What is the relative atomic mass of an element?

A

The mass number of an element

12
Q

How can elements and compounds be detected?

A

Using instrumental methods

13
Q

What are instrumental methods often?

A

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

14
Q

How can artificial colours be detected and identified in foods?

A

Paper chromatography

15
Q

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

A

A pencil because pen ink would run with the water

16
Q

What are examples of instrumental methods?

A

Gas chromatography and mass spectroscopy

17
Q

What does gas chromatography allow?

A

The separation of a mixture of different compounds

18
Q

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

A

Identifying the substance

19
Q

What happens in a gas chromatography column?

A

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

20
Q

What do the different peaks on a gas chromatograph show?

A

The number of compounds present

21
Q

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

A

The retention time

22
Q

What can a mass spectrometer do?

A

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

23
Q

What is the molecular mass given by?

A

The molecular ion peak

24
Q

What can the mass spectrometer also give us?

A

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

25
Q

What is the retention time?

A

The time taken to reach the detector

26
Q

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

A

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

27
Q

What is the first step for calculating the empirical formula?

A

List all the elements in the compound

28
Q

What is the second step for calculating the empirical formula?

A

Underneath, write their masses or percentages given to you

29
Q

What is the third step for calculating the empirical formula?

A

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

30
Q

What is the fourth step for calculating the empirical formula?

A

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

31
Q

What is the fifth step for calculating the empirical formula?

A

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

32
Q

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

A

Write out the balanced symbol equation

33
Q

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

A

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

34
Q

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

A

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

35
Q

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

A

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

36
Q

How do you calculate the percentage yield?

A
actual yield (grams)
                 /                          x 100
predicted yield (grams)
37
Q

What is a reversible reaction?

A

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

38
Q

How can reversible reactions be represented?

A

With an arrow