1.2 amount of substance

Question 1

how many particles are in a mole?

Answer 1

6.022 x 10^23

Question 2

no of particles=

Answer 2

no of moles x avogadros constant

Question 3

moles=

Answer 3

mass/Mr

Question 4

What is the ideal gas equation?

Answer 4

lets you find no of moles in volume at any temp and pressure
pV=nRT
Pa, m^3, mol,8.31JK-1mol-1, k (add 273)

Question 5

what is an ionic equation?

Answer 5

only includes reacting particles and products
1) balance equation
2) rewrite as ions 3)remove anything on both sides
4) check charges are balanced

Question 6

how do you work out calculating masses?

Answer 6

1) write balanced equation
2)work out how many moles of reactant you have
3) use molar ratio to find how many moles of product will be formed
4) calculate mass of product
dont use big nos in Ar as these are taken into account with ratio

Question 7

How do calculate gas volumes?

Answer 7

1) balance equation
2) find moles of reactant
3)use molar ratio to find moles of product
4) put moles of product into ideal gas equation

Question 8

what is a titration?

Answer 8

neutralisation reaction to find conc of acid/ alkali solution

Question 9

2 indicators used in titrations?

Answer 9

methyl orange is red in acid and yellow in alkali
phenolphthalein is colourless in acid and pink in alkali

Question 10

How do you do a titration calculation?

Answer 10

draw table of acid, alkali and conc, vol, mol
fill in what know (vol in dm3
work out moles you can
use molar ratio to find other moles
find conc

Question 11

what is the empirical formula?

Answer 11

smallest whole number ratio of atoms of eahc element in a compound

Question 12

what is the molecular formula?

Answer 12

actual number of atoms in a molecule

Question 13

how do you work out molecular formula from empirical

Answer 13

1) find empirical mass by adding up Ar of each atom eg 83
2) divide molecular mass by empirical eg 166/83=2
3) do empirical formula x answer to 2 eg C4H302 X 2 = C8H604

Question 14

how do you calculate empirical formula?

Answer 14

1) calculate moles of each element by doing % or mass (assume you’ve got 100g of compound) / Ar
2) divide each no of moles by smallest no of moles you found to get the ratio
3) may have to multiply to get whole numbers

Question 15

What is maximum theoretical yield?

Answer 15

the yield you would get assuming no chemicals are lost.

Question 16

how do you work out chemical yield?

Answer 16

% yield = (actual/ theoretical) x100

theoretical- reacting masses

Question 17

what is atom economy?

Answer 17

measure of proportion of reactant atoms that become part of the desired product. reactions have have 100% yield but still low atom economy

Question 18

What can you do with the by-products if dont have 100% atom economy?

Answer 18

sell them

Question 19

Advantages of high atom economy

Answer 19

economic- waste of money if lots of reactant ends up as useless byproduct, lots of money to separate product you want from others, waste products need to be safely disposed of- expensive
environmental and ethical- use raw materials efficiently so they last longer. produce less waste which can be harmful to environ, companies can find easier, cheaper ways to produce medicine etc so sold cheaper

Question 20

How do you work out % atom economy?

Answer 20

(mass of desired products / mass of all reactants) x100
USE big nos when calculating molecular mass

Question 21

What is the limiting reagent?

Answer 21

reactant that is used up first so controls the amount of reaction you get. other reactant is in excess

Question 22

How do you work out the limiting reagent?

Answer 22

determine the number of moles of each reactant
compare molar ratio of reactants with ratio in balanced chem equation to determine which is limiting

Question 23

What is water of crystalisation?

Answer 23

water that is chemically bonded into a crystal structure

Question 24

do anhydrous and hydrated mean?

Answer 24

anhydrous- contains no water of crystallisation-powder
hydrated- contains water of crystallisation- crystal

Question 25

how do you workout water of crystallisation by heating it?

Answer 25

findmass of each component (compound and water) using conservation of mass
find the moles of each
divide by the lowest moles to find the ratio

Question 26

How do you do a TOF calculation?

Answer 26

rearrange Ek=1/2mv^2 to find the velocity of an ion
use t=v/d to find time for ion to travel

combined equation is
t= d x square root of (m/2KE)

may need to use moles=no of particles/ avogadros constant

Question 27

practicals in this topic

Answer 27

titrations

Question 28

why might the experimental value and correct value for X in water of crystallisation be different?

Answer 28

sample wasnt heated until a constant mass