Chapter 4 - The Mole & Volumetric Analysis

Question 1

What is relative atomic mass (of an element)?

Answer 1

The average mass of one atom of the element relative to 1/12 of the mass of a carbon-12 atom

Question 2

What is the symbol for relative atomic mass?

Answer 2

Ar

Question 3

What is the unit for relative atomic mass?

Answer 3

no unit

Question 4

The relative atomic mass of an element takes into account the mass of all the ________ of the element and their ________

Answer 4

isotopes

relative abundance

Question 5

What is relative molecular mass (of a molecule)?

Answer 5

The average mass of one molecule of the element or compound relative to 1/12 of the mass of a carbon-12 atom

Question 6

What is the symbol for relative molecular mass?

Answer 6

Mr

Question 7

What is the unit for relative molecular mass?

Answer 7

no unit

Question 8

What is relative formula mass (of an ionic compound)?

Answer 8

The average mass of one unit of the ionic compound relative to 1/12 of the mass of a carbon-12 atom

Question 9

What is the symbol for relative formula mass?

Answer 9

Mr

Question 10

What is the unit for relative formula mass?

Answer 10

no unit

Question 11

What is molar mass (of an element)?

Answer 11

The mass of one mole of atoms of the element

Question 12

What is the unit for molar mass?

Answer 12

g/mol

Question 13

The molar mass of an element is equal to its ________ in grams

Answer 13

relative atomic mass (Ar)

Question 14

The molar mass of a molecule is equal to its ________ in grams

Answer 14

relative molecular mass (Mr)

Question 15

The molar mass of an ionic compound is equal to its ________ in grams

Answer 15

relative formula mass (Mr)

Question 16

Formula to calculate number of moles

Answer 16

Number of moles = Number of particles / 6.02 x 10^23

Number of moles = Mass (in g) / Molar mass (in g/mol)

Question 17

Formula to calculate percentage composition by mass

Answer 17

Percentage composition by mass = (Ar of the element x Number of atoms of the element in the formula) / Mr of the compound x 100%

Question 18

The empirical formula of a compound shows…

Answer 18

1. the types of elements present in the compound

2. the simplest ratio of the different types of atoms in the compound

Question 19

The molecular formula of a compound shows…

Answer 19

the exact number of atoms of each element in a molecule of the compound

Question 20

The molecular formula is ________ of the empirical formula

Answer 20

always a multiple

Question 21

One mole of any gas occupies a volume of ____ at ________

Answer 21

24dm^3

room temperature and pressure

Question 22

24dm^3 is the ________ of a gas at r.t.p.

Answer 22

molar volume

Question 23

Equal volumes of gases have ________ number of moles and ________ masses

Answer 23

the same

different

Question 24

Formula to calculate number of moles of gas

Answer 24

Number of moles of gas = Volume of gas in dm^3 / 24dm^3

Question 25

What is a limiting reagent?

Answer 25

The reactant that reacts completely and hence limits the amount of product produced

Question 26

Formula to calculate percentage purity of starting reagent

Answer 26

Percentage purity = Pure mass of starting reagent / Total impure mass x 100%

Question 27

Formula to calculate percentage yield of product

Answer 27

Percentage yield = Actual yield / Theoretical yield x 100%

Question 28

What are some possible reasons that the actual yield is often less than the theoretical yield of the product in an experiment?

Answer 28

1. Impure starting reagent 2. Not mixed well 3. Product not entirely collected 4. Spills

Question 29

What is a solution?

Answer 29

A fluid with dissolved substances in it

Question 30

What is a solute?

Answer 30

The dissolved substance in a solution (usually solid)

Question 31

What is a solvent?

Answer 31

The fluid in which the solute dissolves (usually liquid)

Question 32

What is a saturated solution?

Answer 32

A solution with the maximum amount of solute dissolved in it

Question 33

What are factors affecting how much solute can be dissolved in a solvent?

Answer 33

1. Volume of solvent 2. Temperature 3. Solubility of solute

Question 34

What is the concentration of a solution?

Answer 34

The amount of solute in 1 dm^3 of a solution

Question 35

What is the unit for concentration of a solution?

Answer 35

g/dm^3 | mol/dm^3

Question 36

Formula to calculate concentration of a solution

Answer 36

Concentration in g/dm^3 = Mass of solute (in g) / Volume of solution (in dm^3) Concentration in mol/dm^3 = Number of moles of solution / Volume of solution (in dm^3)

Question 37

Formula to calculate concentration of a solution in mol/dm^3 from its concentration in g/dm^3

Answer 37

Concentration in mol/dm^3 = Concentration in g/dm^3 / Molar mass of solute

Question 38

What is titration?

Answer 38

A laboratory technique in which a fixed volume of an unknown solution is reacted with a fixed volume and concentration of a known solution

Question 39

What is the function of titration?

Answer 39

To accurately determine the concentration of an unknown solution

Question 40

What are the apparatus used to measure accurate volumes?

Answer 40

- Pipette (for a solution of fixed volume) | - Burette (for a solution that is added gradually)

Question 41

What is a titrant?

Answer 41

A solution of known concentration | usually filled in the burette

Question 42

What is an analyte?

Answer 42

A solution of unknown concentration (that can be experimentally determined) (usually pipetted into the conical flask)

Question 43

Why is there a need for a suitable pH indicator in an acid-base titration?

Answer 43

- Starting solutions are colourless (unable to tell whether reaction has occurred) - Precipitate is soluble (no indication that reaction has occurred)