Amount of Substance (CDS)

Question 1

What is meant by relative atomic mass?

Answer 1

The average mass of an atom relative to the mass of 1/12 of the mass of an atom of C12

Question 2

What are the units for relative atomic mass?

Answer 2

g mol -1 or grams per mole

Question 3

What is an isotope?

Answer 3

An atom of an element that has the same amount of protons and electrons but a different neutron number

Question 4

Equation used to calculate the Ar from all the isotopes of an atom

Answer 4

(mass of isotope x abundance) / sum of abundances

Question 5

What is meant by relative molecular mass?

Answer 5

The mass of a molecule relative to 1/12 of the mass of an atom of C12

Question 6

What are the units for Mr?

Answer 6

g mol -1 or grams per mole

Question 7

How to calculate Mr

Answer 7

Sum of Ar values of all elements in the molecule

Question 8

What is meant by relative formula mass?

Answer 8

The mass of the formula, relative to 1/12 of the mass of an atom of C12

Question 9

What is the value of the mole?

Answer 9

6.02 x 10^23

Question 10

How much does 1 mole of C12 weigh?

Answer 10

12 grams

Question 11

How much does 0.5 moles of C12 weigh?

Answer 11

6 grams

Question 12

How much does 0.25 moles of C12 weigh?

Answer 12

3 grams

Question 13

How much does 5 moles of C12 weigh?

Answer 13

60 grams

Question 14

Equation the links the value of the mole, number of moles and number of atoms

Answer 14

Number of moles = number of atoms / 6.02 x 10^23

Question 15

Equation that links number of mols, mass and Mr

Answer 15

Mols = mass / Mr

Question 16

What is meant by x H20?

Answer 16

The amount of water relative to one mole of salt in a hydrated salt

Question 17

How to find xH2O

Answer 17

1. find the moles of anhydrous salt
2. find the moles of water
3. Divide by the smallest value to find the ratio

Question 18

What is the unit of concentration?

Answer 18

mol dm-3 or moles per dm3

Question 19

How many cm3 is 1dm3

Answer 19

1000 cm3

Question 20

Equation that links concentration, volume and moles

Answer 20

mols = conc x vol

Question 21

How to find the limiting reagent in a 1:1 ratio

Answer 21

1. Find out mols of each reactant
2. Lower value is the limiting reagent

Question 22

How to find the limiting reagent in a 1:2 ratio

Answer 22

1. Find out mols of each reactant
2. Multiply moles of the 1 reactant by 2
3. If vale of 2 reactant is lower it is the limiting reactant

Question 23

How much space does 1 mol of gas occupy at 1atm and 25 degrees celsius

Answer 23

24 dm3

Question 24

Equation that links 24, volume and moles in relation to gas

Answer 24

vol = mols x 24

Question 25

What is the ideal gas equation

Answer 25

PV = nRT

Question 26

What do the letter stand for in PV = nRT

Answer 26

P = Pressure V = Volume in m3 n= number of moles R = Gas constant T = Temp in Kelvin

Question 27

What is the value of R (gas constant)

Answer 27

8.31 J . K-1 mol-1

Question 28

How to convert from m3 to cm3

Answer 28

x 1 million

Question 29

How to convert from cm3 to m3

Answer 29

divided by 1 million

Question 30

How to convert from m3 to dm3

Answer 30

x 1000

Question 31

How to convert from dm3 to m3

Answer 31

/ 1000

Question 32

Equation for % composition by mass

Answer 32

(molar mass of element in compound / Mr or RFM) x 100

Question 33

Steps to calculate empirical formula from mass of elements/ % composition

Answer 33

1. Divide mass or % comp by the Ar of the element 2. Find the moles of each element 2. Divide by smallest value to get ratio

Question 34

Equation for % atom economy

Answer 34

(molar mass of desired product / molar mass of reactants) x 100

Question 35

Equation for % yield

Answer 35

(actual yield / theoretical yield) x 100

Question 36

Celsius to kelvin

Answer 36

+273

Question 37

kPa to Pa

Answer 37

x 1000

Question 38

What is the empirical formula?

Answer 38

Represent the simplest whole number ratio of the atoms of each element present in a compound

Question 39

Ionic equation for the reaction between acid and alkali

Answer 39

H+ + OH- --> H2O

Question 40

Titration steps to find out the concentration of an alkali:

Answer 40

1. Fill a burette with acid of a known concentration and record how much is in the burette 2. Accurately measure a set amount of the alkali of an unknown concentration using a calibrated pipette and a pipette filler 3. Add the alkali to a conical flask with a suitable indicator 4. Run in acid until colour changes for a rough titre. Record the end point and take it away from the amount there was in the burette at the beginning for the volume of acid that is in the conical flask 5. Empty and wash out conical flask and put the same amount of alkali back into the flask. 6. Run acid into the flask and close the flask to run the acid dropwise when you near the end point 7. Repeat titrations until you get concordant results (within 0.10cm3 of each other)

Question 41

What are titrations used for?

Answer 41

Titrations can be used to find the concentration of an unknown acid or alkali by seeing how much acid or alkali of a known concentration will neutralise it.

Question 42

Phenolphthalein in different conditions

Answer 42

Colourless in acidic conditions, Pink in alkaline

Question 43

Methyl Orange in different conditions

Answer 43

Red in acidic conditions, Yellow in alkaline

Question 44

Finding xH2O

Answer 44

xH2O is an amount of water relative to one mole of a salt. To find xH2O, 1. Find the moles of salt and the moles of water 2. Divide both by the smallest value to get a whole number ratio, and therefore a value for x

Question 45

What is the limiting reagent?

Answer 45

A limiting reagent is the reactant that is entirely consumed during a chemical reaction, and it limits the amount of product that can be formed.

Question 46

Molar gas volume at 1ATM and 25 degrees celsius

Answer 46

1 mole of any gas occupies 24.0 dm3 of space at standard temperature and pressure volume = moles of gas x 24

Question 47

Key assumptions with the ideal gas equation:

Answer 47

1. No intermolecular forces exist between gas molecules 2. Volume occupied by gas molecules is negligible.

Question 48

cm3 to m3

Answer 48

divide by 1 million

Question 49

dm3 to m3

Answer 49

divide by 1000