C3: Quantitative Chemistry

Question 1

What is the idea of the conservation of mass?

Answer 1

the total mass of the products in a reaction is equal to the total mass of the reactants

Question 2

Why is mass conserved?

Answer 2

no atoms are lost or made

Question 3

What is a half equation used for?

Answer 3

to show what happens to one reactant in a chemical reaction, with electrons written as e-

Question 4

What is an ionic equation?

Answer 4

a simplified version of a chemical equation, which just shows the species that are involved in the reaction.

Question 5

What is a species (in chemistry)?

Answer 5

refers to the different atoms, molecules or ions that are involved in a reaction

Question 6

What is the relative formula mass of a compound?

Answer 6

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

Question 7

Why do some reactions appear to have a change in mass?

Answer 7

if a reaction is carried out in a non-closed system and include a gas that can enter or leave

Question 8

What is a mole (mol)?

Answer 8

a measure of the number of particles contained in a substance

Question 9

What is the Avogadro constant?

Answer 9

6.02 x 10^23, the number of particles in one mole of any substance

Question 10

What can balanced equations show and be used for?

Answer 10

-show the number of moles of each product and reactant
-can be used to calculate the mass of the reactants and products

Question 11

What is a limiting reactant?

Answer 11

the reactant that is completely used up in a reaction; it stops the reaction going any further and any further products from being produced

Question 12

At room temperature and pressure, what volume does one mole of a gas occupy?

Answer 12

24 dm^3

Question 13

What do acids and alkalis react together to form?

Answer 13

a neutral solution

Question 14

What is titration?

Answer 14

an accurate technique that can be used to find out how much of an acid is needed to neutralise an alkali

Question 15

What happens in terms of ions, when neutralisation takes place?

Answer 15

the hydrogen ions from the acid join with the hydroxide ions from the alkali to form water

Question 16

Give an example of a suitable indicator for use with a strong acid and strong alkali.

Answer 16

methyl orange or phenolphthalein

Question 17

Give examples of strong acids.

Answer 17

hydrochloric acid, nitric acid, and sulfuric acid

Question 18

Give examples of strong alkalis.

Answer 18

aqueous sodium hydroxide, and aqueous potassium hydroxide

Question 19

Titration can be used to find the concentration of an acid or alkali if which factors are known?

Answer 19

-the relative volumes of the acid and alkali used
-the concentration of the other acid or alkali

Question 20

Why might it not be possible to obtain the calculated amount of product?

Answer 20

-if the reaction is reversible, it might not go to completion
-some product could be lost when it is separated from the reaction mixture
-some of the reactants may react in different ways to the expected reaction

Question 21

What is the yield of a reaction?

Answer 21

the amount of product obtained

Question 22

What is atom economy?

Answer 22

a measure of the amount of reactant that ends up in a useful product

Question 23

What are the two ways that ethanol can be produced?

Answer 23

hydration and fermentation

Question 24

Describe hydration as a method of producing ethanol.

Answer 24

ethene is reacted with steam to form ethanol, has 100% atom economy, it is an addition reaction (all the reactant atoms end up in the desired product)

Question 25

Describe fermentation as a method of producing ethanol.

Answer 25

fermentation of glucose, anaerobic respiration, only about 50% atom economy

Question 26

What factors are considered when choosing a reaction pathway?

Answer 26

-atom economy
-cost of reactants
-percentage yield
-rate of reaction
-equilibrium position
-usefulness of by products