mole calculations and titration

Question 1

what is the conservation of mass

Answer 1

the total mass of the reactants is equal to to the total mass of the products

Question 2

what is the atomic number

Answer 2

the number of protons

Question 3

what is the mass number

Answer 3

the number of protons and neutrons

Question 4

is the relative atomic mass (mass number) at the top or the bottom of an element

Answer 4

top

Question 5

is the atomic number at the top or the bottom of an element

Answer 5

bottom

Question 6

what is the Mr ( or Ar)

Answer 6

relative atomic mass

Question 7

how to work out the Ar

Answer 7

(abundance x relative mass (of atom 1)) + (abundance x relative mass (of atom 2)) / 100

Question 8

what is used to compare the relative atomic mass

Answer 8

standard point reference e.g Carbon - 12
its 12 because it has of 12 units as it has 6 protons and 6 neutrons

Question 9

how to find the Mr

Answer 9

multiply its relative mass by the number of atoms e.g Mr of carbon dioxide ( relative mass of oxygen is 16) ( relative mass of carbon is 12) CO2
16 x 2 = 32 Mr = 32 + 6 = 44

Question 10

how to find the Mr

Answer 10

multiply its relative mass by the number of atoms e.g Mr of carbon dioxide ( relative mass of oxygen is 16) ( relative mass of carbon is 12) CO2
16 x 2 = 32 Mr = 32 + 6 = 44

Question 11

what is a mole

Answer 11

• the measure of the number of particles in a substance

Question 12

what is Avogadro constant

Answer 12

6.02 x 10 23 (10 to the power of 23)

Question 13

what does avogadro constant show

Answer 13

that one mole of any substance contains the same number of particles

Question 14

how to calculate mole

Answer 14

mass / Mr (or Ar)

Question 15

how to find numbers needed to balance an equation using moles

Answer 15

we calculate the moles of each substance the divide the number of moles by the smallest number f moles (this gives the simplest whole number ratio)

Question 16

which one is the limiting reactant in an equation

Answer 16

the one with the least amount of moles

Question 17

which one is in excess in an equation

Answer 17

the one with the most moles

Question 18

how to calculate volume of a gas using moles

Answer 18

moles x 24dm3 (dm cubed)

Question 19

what is concentration measured in

Answer 19

mol/dm3 or g/dm3

Question 20

what is volume measured in

Answer 20

dm3

Question 21

how many cm3 in 1 dm3

Answer 21

0.001

Question 22

how to work out concentration using moles

Answer 22

moles / volume (dm3) OR moles / volume divide 1000 (if the volume is in cm3)

Question 23

how can you increase the concentration

Answer 23

• adding more solute and dissolving it in the same volume of its solution
• evaporating off some of the water from the solution so you have the same mass of solute in a smaller volume of solution

Question 24

factors that affect percentage yield

Answer 24

• if the reaction is reversible it may not go to completion
• some of the product could be lost when its separated from the reaction mixture
• some of the product may be lost in handling or left in the apparatus
• the reactants may not be pure

Question 25

what is the yield

Answer 25

the amount of product obtained

Question 26

how to work out the yield

Answer 26

percentage yield - yield from the reaction / maximum theoretical yield x 100

Question 27

what is the atom economy

Answer 27

the measure of the amount of reactant that end up in a useful product

Question 28

what is the end point

Answer 28

the point at which the alkali and the acid has completely reacted

Question 29

method for tritration

Answer 29

1) wash the volumetric pipette with distilled water and some of the alkali and then measure the volume of the alkali into a conical flask using a volumetric pipette
2) add a few drops of an indicator (in this case phenolphthalein) in the conical flask and swirl
3) rinse a burette with some distilled water and acid then pour the acid in the burette, use the markings on the burette to measure the volume and use the bottom of the meniscus to read the volume
4) record the reading of the burette, then use the tap to release small amounts of acid into the conical flask - swirl the acid to make sure the solutions are mixed
5) repeat step 4 until the indicator has changed to a sharp colour this shows the end point, record the reading of the burette and work out the volume in the acid - this volume is known as the titre
6) repeat this experiment 3 times and discard any anomalous results until you eventually get two results 0.1 dm3 within each other these results are called concordant
7) calculate the concentration of the alkali in mol/dm3

Question 30

how to work out atom economy

Answer 30

mass of atoms in desired product/mass of atoms in product x100

Question 31

what colour is litmus paper in acid

Answer 31

red

Question 32

what colour is methyl orange in acid

Answer 32

red

Question 33

what colour is phenolphthalein in acid

Answer 33

colourless

Question 34

what colour is phenolphthalein in alkali

Answer 34

pink

Question 35

what colour is litmus in alkali

Answer 35

blue

Question 36

what colour is methyl orange in alkali

Answer 36

yellow

Question 37

how to work out concentration without moles

Answer 37

mass / volume

Question 38

what is atom economy important for

Answer 38

• economic reasons
• sustainable development as more products are made and less waste is produced
• to conserve the earths resources to minimise pollution

Question 39

what is the volume of any gas at room temperature and pressure

Answer 39

24 dm3