Topic 3: Quantitative Chemistry ✅

Question 1

What is the Law of Conservation of Mass equation?

Answer 1

The total mass of reactants equal the total mass of products

Question 2

How do you calculate the relative formula mass of a compound?

Answer 2

By adding the relative atomic masses of the elements that make the compound and then multiply it by the number of atoms of that element in the compound, then add the numbers together.

Question 3

What is the law of conservation of mass?

Answer 3

A law that states that no atoms can be created or destroyed in a chemical reaction.

Question 4

What is relative atomic mass?

Answer 4

The average mass of the atom.

Question 5

What is another name for the relative formula mass of a compound?

Answer 5

Relative molecular mass

Question 6

How does burning of wood change the mass of products?

Answer 6

It decreases it as carbon dioxide and water (and other gases) is released.

Question 7

Give 3 example of how the mass of the product can change?

Answer 7

Burning wood
Corrosion if metals
Zinc+Hydrochloric acid

Question 8

Every chemical measurement involves some…

Answer 8

… uncertainty

Question 9

How can you reduce uncertainty?

Answer 9

By repeating the measurement from experiments several times and calculating an average from them.

Question 10

Why must chemical equations be balanced?

Answer 10

To make sure that there are the same number or atoms of an element before and after a reaction.

Question 11

What does the molecular formula show?

Answer 11

The actual amount of atoms which make up a molecule.

Question 12

Name an example of a molecular formula.

Answer 12

Glucose C6H12O6

Question 13

What does Empirical formula show?

Answer 13

The simplest ratio of atoms which make up a molecule.

Question 14

Name and example of empirical formula.

Answer 14

Glucose CH2O

Question 15

What are moles?

Answer 15

A measurement if chemical amounts.

Question 16

One mole is a substance is ____ atoms of that substance.

Answer 16

6.02 X 10 to the power of 23

Question 17

What is the number 6.02 X 10 to the power of 23 known as in terms of moles?

Answer 17

Avogadros Constant

Question 18

The relative formula mass of a substance is equal to the mass of…

Answer 18

1 mole of that substance

Question 19

How do you calculate relative formula mass?

Answer 19

The sum of the relative atomic mass of the elements X number of atoms in elements

Question 20

What is the equation for using moles to balance equations?

Answer 20

Moles=mass/relative formula mass

Question 21

What is a limiting reactant?

Answer 21

The reactant that is completely used up and therefore stops the reaction.

Question 22

What 2 things do you need to know to work out the moles of a substance?

Answer 22

-Mass
-Mr

Question 23

How do we make sure there is no acid left after the reaction when neutralising and acid?

Answer 23

Use an excess amount of the other reactant.

Question 24

What can we use to calculate the number of moles when a substance is dissolved in a solution?

Answer 24

We can use the solutions concentrations.

Question 25

What 2 units is concentration measured in?

Answer 25

G/dm3 Mol/dm3

Question 26

The percentage yield for any reaction is always less than…

Answer 26

…100%

Question 27

What 4 factors make sure the percentage yield of reactions stays below 100%?

Answer 27

Incomplete Reactions Waste Extraction Side Reactions

Question 28

What 2 reasons may a reaction be incomplete?

Answer 28

-It is very slow and may not be given enough time to happen -The reaction is reversible and some of the products have been converted back into reactants

Question 29

How does waste make sure the percentage yield stays below 100%?

Answer 29

Some of the chemicals will remain stuck to the apparatus and will be wasted.

Question 30

How does extraction make sure the percentage yield stay below 100%?

Answer 30

It might be difficult to fully separate the product from the reaction mixture.

Question 31

How do side reactions make sure the percentage yield stays below 100%?

Answer 31

Unexpected reactions can happen, which mean that the intended product is not created.

Question 32

What is real yield?

Answer 32

The mass of a desired product obtained from a reaction.

Question 33

What is theoretical yield?

Answer 33

The maximum mass of a product that could possibly be created from a reaction.

Question 34

What can theoretical yield be calculated from?

Answer 34

A balanced equation if we know the mass of the reactants.

Question 35

How is percentage yield of a reaction calculated?

Answer 35

Real yield / theoretical yield X 100

Question 36

What is percentage yield?

Answer 36

A comparison of the real and theoretical yields of a reaction.

Question 37

Why are reaction pathways with high atom economies good (2 reasons)?

Answer 37

Cost effectiveness Low waste

Question 38

What 6 things should you consider when selecting a reaction pathway?

Answer 38

-Atom economy -How much the reactants will cost -What the percentage yield will be -How quickly the reaction will happen -How useful the by-products of the reaction are -The position of the equilibrium

Question 39

What 2 things can the concentration of a solution be measured in terms of?

Answer 39

Moles Mass

Question 40

What 2 things do we have to know to calculate the amount of a solute in a solution?

Answer 40

The concentration of the solution The volume of the solution

Question 41

What is a solute?

Answer 41

A dissolved substance

Question 42

What 2 things do we need to know in order to calculate the concentration of a solution?

Answer 42

The volumes of 2 solutions that react completely The concentration of 1 of these solutions

Question 43

If the temperate and pressure conditions are the same, the same amounts of any gases (when measured in moles) will take up…

Answer 43

…Identical volume