chapter 3

Question 1

what is one mole

Answer 1

one mole of a substance is the amount of substance which contain as many formula units as there are atoms in 12g of carbon 12. 6.02 x 10^23

Question 2

units of mol

Answer 2

g mol^-1

Question 3

moles equation

Answer 3

moles = mass/molar mass

Question 4

what is molecular formula?

Answer 4

number of atoms of each element in a compound

Question 5

what is emperical formula

Answer 5

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

Question 6

when is emperical formula used?

Answer 6

when substances arent molecules and instead exist as giant crystaline structure

Question 7

what is relative molecular mass

Answer 7

mr - compares mass of a molecule w the mass of a carbon 12 atom

Question 8

how is relative formula mass different to relative molecular madd?

Answer 8

it is the total atomic mass for an emperical formula compound

Question 9

how to calculate emperical formula from mass?

Answer 9

convert mass into moles, divide the moles by the value w the smallet moles

Question 10

how to calculate molecular formula from percentages?

Answer 10

percentage/Mr
divide moles of each value by the smallest mole
then do the relative molecular mass/mr of emperical formula
take the value and times it by the emperical formula e.g. ch2o x 6 = c6h12o6

Question 11

why are coloured crystals said to be hydrated?

Answer 11

water is a part of there structure

Question 12

anhydrous

Answer 12

when water is removed, turns white

Question 13

why is getting the formula from an experiment not always accurate?

Answer 13

• assumes all water has been lost (if colour change is little its hard to tell when al water is lost, so keep heating till mass no longer changes)
• assumes there is no further decomposition (salts decompose and change colour when heated, so its hard to judge colour change)

Question 14

1cm3 in ml

Answer 14

1ml

Question 15

1 dm3 in cm3

Answer 15

100cm3

Question 16

1 dm3 in ml

Answer 16

1000 ml

Question 17

1 dm3 in l

Answer 17

1l

Question 18

concentration equation

Answer 18

n=c x v

Question 19

what is a standard solution?

Answer 19

a solution of known concentration

Question 20

how is standard solution produced?

Answer 20

dissolving an exact mass of solute in a solvent making the solution to an exact volume

Question 21

how to work out standard solution calc

Answer 21

find mol of substance using n = c x v
use m=n x mr to find mass that needs to be dissolved

Question 22

what is molar gas volume?

Answer 22

Vm - volume per mole pf gas molecules at a stated temperature and pressure

Question 23

what is STP

Answer 23

standard temperature and pressure

Question 24

what is RTP

Answer 24

room temperature pressue, 24 dm3 mol^-1
20 c and 101 kpa

Question 25

molar gas volume equation

Answer 25

moles = volume/Vm
if dm3 24
if cm3 24000

Question 26

limitations of RTP

Answer 26

conditions are not always room temperature and pressure

Question 27

ideal gas equation

Answer 27

pV = nRT

Question 28

units for ideal gas equation

Answer 28

p - pressure pa
V - volume m3
n - mol
R - gas constant - 8.34jmol-1k-1
T - tem - kelvin

Question 29

cm3 to m3
dm3 to m3
c to k
kpa to pa

Answer 29

x 10^-6
x10^-3
+273
x 10^3

Question 30

what is the ratio of balanced equations called?

Answer 30

stoichemotry

Question 31

percentage yield equation

Answer 31

actual yield/theoretical yield x 100

Question 32

why is theoretical yield less than actual yield?

Answer 32

reaction not gone to completion
side reactions may have taken place
purification of product may mean loss of some product

Question 33

what is atom economy used for?

Answer 33

measure of how well atoms have been utilised

Question 34

atom economy equation

Answer 34

mr of desired product/mr of all products x 100

Question 35

why is high atom economy important?

Answer 35

produce large proportion of desired product
sustainability make best use of natural resources