Unit 2: 3 - How Much?

Question 1

What is the relative mass of protons and neutrons?

Answer 1

1

Question 2

What do we call the total amount of protons and neutrons in an atom?

Answer 2

Its mass number

Question 3

What do we call the total amount of protons in the atom?

Answer 3

The atomic (or proton) number

Question 4

In a neutral atom, how many electrons are there compared to protons?

Answer 4

The same amount

Question 5

What is the name given to an atom with an irregular number of neutrons?

Answer 5

An isotope

Question 6

What is the relative charge of each of the 3 components of an atom?

Answer 6

Proton +1 Neutron 0 Electron -1

Question 7

What is the relative mass of an electron?

Answer 7

0

Question 8

What do we call an atom with a positive or negative charge?

Answer 8

An ion

Question 9

What is special about some isotopes?

Answer 9

There are unstable and radioactive?

Question 10

What is a mole?

Answer 10

The relative atomic mass in grams.

Question 11

What is the relative atomic mass and its symbol?

Answer 11

The Ar is the relative mass of 1 atom of the element.

Question 12

What is the relative molecular mass and its symbol?

Answer 12

The Mr is the total sum of all the Ars in the atom.

Question 13

How do you work out the percentage of mass used by a single element in a molecule?

Answer 13

(Total number of that element * Relative atomic mass of the element) / Relative molecular mass (*100)

Question 14

What is the empirical formula?

Answer 14

The simplest ratio of the atoms or ions in a compound. For example, the molecular formula of ethane is C2H6 but its empirical formula is CH3.

Question 15

How do we work out a more complicated empirical formula? E.g. What is the empirical formula when 3.2g of sulfur reacts with oxygen to make 6.4g of sulfur oxide? (The atomic mass of sulphur is 32g and oxygen is 16g

Answer 15

Question 16

What is the yield of a chemical reaction?

Answer 16

The yield is how much you make.

Question 17

What is the percentage yield?

Answer 17

The percentage yield compared the amount made with the amount that could be made.

Question 18

How do we calculate the percentage yield?

Answer 18

(Amount of product collected / Maximum amount of product possible) *100

Question 19

Why is it not usually possible to get the maximum yield from a reaction?

Answer 19

Reactions may not be fully completed, other reactions might happen and some product may be lost when separated or collected.

Question 20

Why should chemical manufacturers use reactions with high yields?

Answer 20

To waste as little energy as possible, making production more sustainable and reducing pollution.

Question 21

What is a reversible reaction?

Answer 21

A reaction which can go both ways.

Question 22

What is an example of a reversible reaction?

Answer 22

Heating ammonium chloride.

Question 23

Give 2 methods used to analyse chemicals in food.

Answer 23

Paper chromatography and mass spectrometry

Question 24

What is gas chromatography?

Answer 24

When the mixture is carried up by a gas through a long column packed with particles of a solid. The individual compounds travel at different speeds and come out at different times. The retention times can be compared with the results known for other compounds to help identify the compounds in the mixture.

Question 25

What can the output from a gas spectrometer be linked to?

Answer 25

A mass spectrometer (which can give further data that a computer can use quickly to identify the individual compounds.

Question 26

What other information can a mass spectrometer give?

Answer 26

It can give the relative molecular mass of a compound. For an individual compound the peak with the largest mass corresponds with to an ion with just one electron removed.