3.1.2 Amount of Substance

Question 1

Ar = ?

Answer 1

Average mass of one atom of an element / 1/12 the mass of one atom of 12-C

Question 2

Mr = ?

Answer 2

Average mass of one molecule / 1/12 the mass of one atom of 12-C

Question 3

What does Ar stand for?

Answer 3

Relative atomic mass.

Question 4

What does Mr stand for?

Answer 4

Relative molecular mass or relative formula mass.

Question 5

How to find relative formula mass?

Answer 5

Sum of all the Ars of the atoms present.

Question 6

What is the Avagadro constant the same as?

Answer 6

Number of particles in a mole.

Question 7

What is the Avagadro constant and where does it come from?

Answer 7

6.022 x 10^23, number of atoms in 12g of 12-C.

Question 8

moles = ?

Answer 8

mass / Mr

Question 9

What does the concentration of a solution tell us, what are the units?

Answer 9

How much solute is present in a known volume of solution, moldm^-3.

Question 10

What is the equation for moles using concentration?

Answer 10

moles = concentration x volume / 1000

Question 11

What is the ideal gas equation?

Answer 11

PV = nRT

Question 12

Define empirical formula.

Answer 12

The empirical formula represents the simplest whole number ratio of the atoms of each element present in a compound.

Question 13

What are the steps to finding the empirical formula?

Answer 13

1) Find masses of each element
2) Find no. of moles of atoms of each element, moles = mass / Mr
3) Convert into a whole number ratio

Question 14

Define molecular formula.

Answer 14

The actual number of atoms of each element in a compound.

Question 15

How do you find the molecular formula?

Answer 15

Relative molecular mass / relative mass of empirical formula

Question 16

What do ionic equations do?

Answer 16

Simplify the equation by considering the ions present.

Question 17

What are spectator ions?

Answer 17

Ions that cancel out on both sides of an ionic equation.

Question 18

% atom economy = ?

Answer 18

(mass of a desired product / total mass of reactants) x 100

Question 19

What does % atom economy tell us in theory?

Answer 19

How many atoms must be wasted in a reaction.

Question 20

What does yield tell us?

Answer 20

The practical efficiency of the process, how much is lost by the practical process or reactions that don’t go to completion.

Question 21

Yield = ?

Answer 21

(no. of moles of product / theoretical moles of product) x 100
OR
(grams of product / theoretical max grams) x 100

Question 22

Why do ionic compounds have high m.ps?

Answer 22

Oppositely charged ions, strong attraction between ions.

Question 23

When finding % atom economy from an equation what values do we take?

Answer 23

The Mrs.

Question 24

When doing calculations what do you need to double check?

Answer 24

All values are correct and SI, know what compound the mole value is attached to.

Question 25

Conversion from cm^3 to m^3?

Answer 25

x10^-6