2.1 atoms and reactions

Question 1

what’s an isotope?

Answer 1

atoms of the same element with a different number of neutrons and different masses
eg carbon-12 and carbon-14

Question 2

what’s the charge of a proton, electron and neutron?

Answer 2

+1
-1
0
respectively

Question 3

define relative isotopic mass

Answer 3

the mass of an isotope compared to 1/12th the mass of carbon-12

Question 4

define relative atomic mass

Answer 4

the weighted* average mass of an atom compared to 1/12th the mass of carbon-12

*weighted - takes into consideration the abundance of each isotope

Question 5

formula for relative atomic mass?

Answer 5

Ar = (isotope mass x %*) + (isotope mass x %) / 100

*% abundance of each isotope

Question 6

describe how you form an ionic equation

Answer 6

split each ionic compound into its ions, except the solids!

cross out ions that appear on both sides of the equations

write out the remaining ions and compounds

Question 7

what’s the value of avogadros constant?

Answer 7

Na = 6.02 x10^23

Question 8

how do you calculate the number of particles? (incl. no. of atoms and ions)

Answer 8

no. of particles = moles x Na

Question 9

how many particles in 1 mole of Fe?

Answer 9

moles x Na
1 x 6.02 x10^23

= 6.02 x10^23 particles

Question 10

what might you use mass spectrometry to determine? name 2 things

Answer 10

the relative isotopic masses and relative abundances of the isotope

calculating the relative atomic mass of an element from the abundances of its isotopes

Question 11

what’s molar gas volume?

Answer 11

gas volume per mole (unit: dm^3 mol^–1)

Question 12

what’s empirical formula?

Answer 12

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

Question 13

how do calculate the empirical formula?

Answer 13

divide the mass or percentage by the Mr to find the moles (for each element)

divide all molar values by the lowest value of moles from the atoms in the element

multiply up to get ‘whole numbers’
eg 1.33 x 3 or 1.25 x 4 or 2.5 x 2
multiply each value by the same number

Question 14

define molecular formula

Answer 14

the amount of atoms in each element in a molecule eg C2H4 - (not simplified to the lowest ratio)

Question 15

what does structural formula show?

Answer 15

it shows how the compound would be drawn out

eg C3H5COOH - the different elements aren’t collected together but they are spread out to show how it would be drawn structurally

Question 16

what’s a hydrated salt?

Answer 16

a salt with water trapped in the ionic lattice

Question 17

what is ‘water of crystallisation’?

Answer 17

the water trapped in a salt during the crystallisation process

Question 18

how do you dehydrate a salt?

Answer 18

evaporate water

Question 19

what do you call a salt that has has the water evaporated out of it?

Answer 19

an anhydrous salt

Question 20

give the equation involving moles, mass and Mr

Answer 20

mass = moles x Mr

Question 21

if you’re given the volume of a gas, how would you find the moles? (equation)

Answer 21

moles = volume / 24
or for cm^3

moles = v / 24000

Question 22

name the equation involving moles conc and vol

Answer 22

moles = concentration x volume

Question 23

name the ideal gas equation

Answer 23

pV = nRT

Question 24

what’s the gas constant?

Answer 24

8.314

Question 25

what’s the pressure and temp at RTP?

Answer 25

101325 Pa or 1 atm 298 K or 25 degrees C

Question 26

how do you convert from cm^3 to dm^3?

Answer 26

divide by 1000

Question 27

how do you convert from dm^3 to m^3?

Answer 27

divide by 1000

Question 28

how do you convert from degrees C to kelvin?

Answer 28

add 273 to degrees C

Question 29

define percentage yield

Answer 29

the amount (mass or moles) of product obtained compared to the theoretical yield of product

Question 30

how do you calculate percentage yield?

Answer 30

actual yield/theoretical x 100

Question 31

define atom economy

Answer 31

how much of the reactants were wasted / how much of the products were useful

Question 32

how to we calculate atom economy?

Answer 32

Mr of desired products/Mr of all product x 100

Question 33

what do we have to take into account when calculating the Mr of something to find atom economy?

Answer 33

the large number infront of atoms or molecules. e.g. the Mr of 2H₂ = 4 NOT 2

Question 34

define acid

Answer 34

a substance that releases H+ ions in an aqueous solution

Question 35

``` whats the formula for: hydrochloric acid? sulphuric acid? nitric acid? ethanoic acid? ```

Answer 35

hydrochloric acid: HCl sulphuric acid: H₂SO₄ nitric acid: HNO₃ ethanoic acid: CH₃COOH

Question 36

whats the difference between strong and weak acids?

Answer 36

strong acids completely disassociate and release all H+ ions. eg HCl --> H+ + Cl- but, weak acids only partially disassociate and only release some H+ ions e.g. CH₃COOH --> CH₃COO- + H+

Question 37

what is a base?

Answer 37

a substance that accepts H+ ions will neutralise an acid does not dissolve in water

Question 38

whats an alkali?

Answer 38

a substance that releases OH- ions in an aqueous solution

Question 39

whats the formula for: sodium hydroxide? potassium hydroxide? ammonia?

Answer 39

sodium hydroxide: NaOH potassium hydroxide: KOH ammonia: NH₃

Question 40

acid + metal carbonate ?

Answer 40

acid + metal carbonate ➝ metal salt + water + carbon dioxide

Question 41

metal + acid ?

Answer 41

metal + acid ➝ metal salt + hydrogen

Question 42

metal oxide + acid ?

Answer 42

metal oxide + acid ➝ salt + water

Question 43

metal hydroxide + acid ?

Answer 43

metal hydroxide + acid ➝ salt + water

Question 44

define anhydrous

Answer 44

a term used to describe a substance with no water

Question 45

what does hydrated mean in relation to salts?

Answer 45

a hydrated salt means there are water molecules trapped in the giant ionic lattice of the salt

Question 46

what is an oxidation number/oxidation state?

Answer 46

the number electrons an atom uses to bond with atoms of other elements.

Question 47

whats the oxidation number of an uncombined element? e.g. C, O₂ or Na

Answer 47

0

Question 48

whats the oxidation number of oxygen (mostly all the time)?

Answer 48

-2

Question 49

whats the oxidation number of oxygen in peroxides (O₂-2)?

Answer 49

-1

Question 50

whats the oxidation number of hydrogen (mostly always)?

Answer 50

+1

Question 51

whats the oxidation number of hydrogen in a metal hydride?

Answer 51

-1

Question 52

whats the oxidation number of a monatomic ion?

Answer 52

the charge of the ion. e.g. Na+1 would have an oxidation number of +1

Question 53

what does the charge of a molecular ion tell you about the oxidation number?

Answer 53

the charge tells you the overall oxidation number. the oxidation numbers of the atoms in the molecular ion will add to this number. eg SO₂-2 - the oxidation no. of the molecular ion = -2 so the oxidation no.s of S and O₂ will add to -2

Question 54

what does a roman numeral tell you about an atom?

Answer 54

``` tells you the magnitude(value) of the oxidation number. eg Fe(II) would have an oxidation number of +2 ```

Question 55

what is the oxidation number of sulphur in a sulfate(IV) ion?

Answer 55

+4

Question 56

what is the oxidation number of nitrogen in a nitrate(III) ion?

Answer 56

+3

Question 57

what is oxidation in terms of electron transfer?

Answer 57

oxidation is the loss of electrons OIL

Question 58

what is reduction in terms of electron transfer?

Answer 58

reduction is the gain of electrons RIG

Question 59

what is oxidation in terms of oxidation number?

Answer 59

oxidation is an increase in oxidation number

Question 60

what is reduction in terms of oxidation number?

Answer 60

reduction is the decrease in oxidation number

Question 61

in reactions, are metals usually oxidised or reduced? why?

Answer 61

metals are oxidised because they lose electrons to become positive ions

Question 62

in reactions, are non-metals usually oxidised or reduced? why?

Answer 62

non-metals are reduced because they gain electrons to become negative ions

Question 63

what is an oxidising agent?

Answer 63

something that accepts electrons it oxidises something and reduces it self because it gains electrons

Question 64

what a reducing agent?

Answer 64

something that donates electrons it reduces something and oxidises itself because it loses electrons