Amount of substance

Question 1

Avogadro’s constant

Answer 1

6.02 x 10^23

Question 2

define molar mass

Answer 2

the mass (in g) of 1 mol of atoms of an element
- it’s equal to its relative atomic mass

Question 3

define empirical formula

Answer 3

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

Question 4

define molecular formula

Answer 4

the number and type of atoms of each element in a molecule

Question 5

define anhydrous

Answer 5

Not containing water molecules

Question 6

define hydrated

Answer 6

Containing water molecules

Question 7

define water of crystallisation

Answer 7

Water molecules attached to the crystal

Question 8

moles equation

Answer 8

n=m/Mr

Question 9

conc equation

Answer 9

n = cv

Question 10

to convert from cm3 to dm3

Answer 10

divide by 1000

Question 11

what are titrations used for

Answer 11

to determine unknown concentrations

Question 12

units of conc

Answer 12

moldm-3 or gdm-3

Question 13

ideal gas equation

Answer 13

• pV = nRT
• p - pressure (Pa)
• V - volume (m3)
• T - temperature (K)
• n - moles
• R - gas constant (8.314 JK-1mol-1

Question 14

at RTP, 1 mole of gas molecules has a volume of

Answer 14

24dm3

Question 15

what’s room temp and pressure (RTP)

Answer 15

• 20C
• 100 kPa
• 1 atm

Question 16

equation for molar gas volume, Vm (ONLY WORKS AT RTP)

Answer 16

n = v/ 24dm3

Question 17

define percentage yield

Answer 17

a measure of the % of reactants that have been converted into the desired product

Question 18

define atom economy

Answer 18

a measure of the proportion of atoms from the reactants that form the desired products

Question 19

equation for percentage yield

Answer 19

(actual no of moles of desired products)/ (theoretical no of mol of desired products) x 100

Question 20

equation for atom economy

Answer 20

(Mr of desired product)/ (sum of reactant Mrs) x 100
- MULTIPLIERS INCLUDED IN CALCULATION

Question 21

what are the ethical, environmental and economic benefits of high atom economy?

Answer 21

fewer raw materials are needed so it is more sustainable, chemical waste is minimised, more efficient, and less money is spent on separation processes

Question 22

what’s a gas syringe and what can it be used for

Answer 22

volumes of gas, either given off by or delivered to experiments
- can be used to find the Mr of a volatile liquid or of an unknown metal

Question 23

conversion from C to K

Answer 23

+273

Question 24

conversion from dm3 to m3

Answer 24

divide by 1000 (x10^-3)

Question 25

conversions from cm3 to dm3 to m3

Answer 25

• cm3 (divide by 1000) = dm3
• dm3 ( divide by 1000) = m3

Question 26

when calculating empirical formula when you get thirds in the ratio you…

Answer 26

x3

Question 27

when calculating empirical formula when you get halves in the ratio you…

Answer 27

x2

Question 28

why is a % yield less than 100% often obtained

Answer 28

• products lost during the isolation procedure (spillages, product stuck on filter paper, lost during liquid transfer)
• reversible reaction
• unwanted by-products