Chapter 2 - amount of substance

Question 0

What is Mr?

Answer 0

The sum of the Ar’s of individual atoms in the compound found on the periodic table

Question 1

Define the term relative molecular mass

Answer 1

The average mass of that molecule compare to 1/12 the mass of a carbon 12 atom

Question 2

Define the term Avogadro’s constant

Answer 2

The number of atoms in 12g of carbon-12

Question 3

What is Avogadro’s number?

Answer 3

6.02*10^23

Question 4

Define the term mole

Answer 4

The amount of a substance that contains Avogadro’s number of particles

Question 5

Define the term empirical formula

Answer 5

The simplest whole number ratio in which the atoms in a compound combine together

Question 6

What is the ideal gas equation?

Answer 6

PV=nRT

Question 7

What are the units for PV=nRT?

Answer 7

P - Pa, V - m^3, n - mol, R - J/mol/K, T - K

Question 8

What does PV=nRT stand for?

Answer 8

P - pressure, V - volume, n - number of moles, R - gas constant (8.31), T - temperature

Question 9

How do you convert celcius to kelvin?

Answer 9

Add 273

Question 10

How do you convert kelvin to celcius?

Answer 10

take away 273

Question 11

How do you convert cm^3 to m^3?

Answer 11

divide by 1000000

Question 12

How do you convert dm^3 to m^3?

Answer 12

divide by 1000

Question 13

How do you convert cm^3 to dm^3?

Answer 13

divide by 1000

Question 14

What is the formula relating mass, Mr and moles?

Answer 14

mass=Mr*mole

Question 15

What are the stages in calculating empirical formula? (and then molecular?)

Answer 15

Find the masses/percentages, divide each mass by corresponding Ar, divide by the smallest, round (and double/triple for molecular formula)

Question 16

How do you get molecular formula from empirical formula when both Mr’s are given/ calculated?

Answer 16

Divide molecular Mr by empirical Mr and times each number of atoms by it

Question 17

Define the term molecular formula

Answer 17

A formula that tells us the numbers of atoms of each different element that makes up a molecule of a compound

Question 18

What is the last thing you do with any equation?

Answer 18

Include units and double check

Question 19

What is the formula relating concentration, moles and volume?

Answer 19

mol=conc*vol

Question 20

What are the units for mol=conc*vol?

Answer 20

mol, mol/dm^3, dm^3

Question 21

What do you need to set up when doing a neutralisation calculation?

Answer 21

A table with mol, conc and vol down the left side and reactants at the top

Question 22

What is the formula for percentage yield?

Answer 22

(actual/theoretical)*100

Question 23

What is the formula for atom economy?

Answer 23

(useful/total)*100

Question 24

Why could there be a low percentage yield?

Answer 24

Not all reactant react - impurities left

loss of reactants - filtering/transferring