Chapter 3 - Amount of substance

Question 1

What is the Avogadro constant?

Answer 1

6.02 x 10^23

Question 2

The equation for the number of moles

Answer 2

Mass / Mr

Question 3

What is the molar mass?

Answer 3

The mass of one mole of something

Question 4

How to work out the number of moles of something?

Answer 4

Multiply the number of moles by the Avogadro constant

Question 5

What is the molar gas volume?

Answer 5

The space that one mole of a gas occupies at room temperature and pressure

Question 6

The equation for the number of moles of a gas

Answer 6

Volume (dm3) / 24 dm^3

Question 7

What is the empirical formula

Answer 7

The smallest whole number of atoms of each element in a compound

Question 8

What is the molecular formula?

Answer 8

The actual number of atoms of each element in a compound

Question 9

Formula of nitrate

Answer 9

NO3 -

Question 10

Formula of carbonate

Answer 10

CO3 2-

Question 11

Formula of sulfate

Answer 11

SO4 2-

Question 12

Formula of hydroxide

Answer 12

OH-

Question 13

Formula of ammonia

Answer 13

NH4 +

Question 14

Formula of zinc

Answer 14

Zn 2+

Question 15

Formula of silver

Answer 15

Ag +

Question 16

What is important to remember about ionic compounds?

Answer 16

The charges always balance

Question 17

What is produced when acids and bases react?

Answer 17

Water and a salt

Question 18

What is the water of crystallisation?

Answer 18

The water in an ionic lattice

Question 19

How to work out the water of crystallisation?

Answer 19

Use COMMA R (see cards)

Question 20

What is the empirical formula of a compound?

Answer 20

The smallest whole number ratio of atoms in a compound

Question 21

What is the molecular formula of a compound?

Answer 21

The actual number of atoms of each element in a molecule

Question 22

How to calculate the empirical and molecular formula?

Answer 22

Use EMMA and COMMA R

Question 23

What is relative molecular mass?

Answer 23

The mass of a molecule compared to the mass of an atom of carbon 12

Question 24

What is the relative formula mass?

Answer 24

Compares the mass of a formula unit with the mass of an atom of carbon-12

Question 25

What is the water of crystallisation?

Answer 25

The water molecules that are part of the crystalline structure of a salt

Question 26

Assumptions made when using experimental formula (2)

Answer 26

All of the water has been lost | No further decomposition

Question 27

What is a polyprotic acid?

Answer 27

One which donates more than one proton

Question 28

What is the ideal gas equation?

Answer 28

Pressure x volume = moles x ideal gas constant x temperature

Question 29

What is the ideal gas constant?

Answer 29

8.31 Jmol-1K-1

Question 30

How to go from cm3 to m3?

Answer 30

x10(-6)

Question 31

How to go from dm3 to m3?

Answer 31

x10(-3)

Question 32

How to go from Celsius to Kelvin?

Answer 32

+273

Question 33

How to go from kPa to Pa?

Answer 33

x10(3)

Question 34

What is stoichiometry?

Answer 34

The ratio of the moles of each reacting substance

Question 35

Reasons why maximum theoretical yield is rarely reached (3)

Answer 35

The reaction may not have gone to completion Side reactions may have taken place as well Purifying the product may result in the loss of some of it

Question 36

Equation for percentage yield

Answer 36

(Actual yield/theoretical yield) x 100

Question 37

What is the limiting reagent?

Answer 37

The one that will be used up first and stop the reaction

Question 38

How to find the limiting reagent?

Answer 38

Work out the moles of each reagent and compare with the equation

Question 39

What is atom economy?

Answer 39

The proportion of atoms in the reagents that end up as the products

Question 40

Equation for atom economy

Answer 40

(Mr of desired product / Mr of all products) x100

Question 41

What is a standard solution?

Answer 41

One with a known concentration

Question 42

How would you work out the formula of a hydrated salt?

Answer 42

1) Weigh an empty crucible 2) Add the hydrated salt into it and weigh again 3) Heat the crucible and contents strongly for about 3 minutes 4) After leaving to cool, reweigh the crucible and remaining salt

Question 43

Why aren't experiments to determine the water of crystallisation always accurate?

Answer 43

They assume that all of the water has been lost and that there is no further decomposition after heating

Question 44

What is the ideal gas equation?

Answer 44

pV = nRT