Chem Unit 1 (Amount of substance) Flashcards Preview

AS Level > Chem Unit 1 (Amount of substance) > Flashcards

Flashcards in Chem Unit 1 (Amount of substance) Deck (38)
Loading flashcards...
1
Q

Relative atomic mass

A

average mass of an atom of an element/ 1/12 of a mass of carbon-12
Number of protons and neutrons added together

2
Q

Relative molecular mass

A

average mass of a molecule/ 1/12 of the mass of an atom of carbon-12
add together the number of atoms in each element in a molecule

3
Q

Relative formula mass

A

mass of the formula unit (ratio of each type of atom in a lattice)
adding the number of atoms of each element in the lattice

4
Q

Avogadro’s constant

A

number of atoms in 12g of carbon-12
6.023 x 10 23
a mole of particles contains 6.023 x 10 23 particles.

5
Q

How do you use Avogadro’s constant?

A

To work out the number of moles of a substance you times the mass of a single atom x Avogadro’s constant.

6
Q

How do you work out the mass of a single atom?

A

Example: 1 H - You would add together 1 proton and 1 electron
1 H + - You would add together 2 protons
3 H - You would add 2 neutrons and 1 proton
If it just asks yo to work out the MASS you don’t need to times by the Avogadro’s constant next.
If it gives you Mr moles = mass / Mr

7
Q

Empirical formula

A

Simplest whole number ratio of atoms of each element in a compound.

8
Q

Molecular formula

A

Actual number of atoms of each element in a compound.

9
Q

How do you work empirical and molecular formula out?

A

Empirical: Divide % or given mass by atomic mass
Divide by smallest number to get simplest ratio
Molecular: Divide Mr of whole thing (given) by the Mr of empirical formula (Atomic masses of each of the elements in the compound.

10
Q

What is percentage yield?

A

actual yield / theoretical yield x 100

11
Q

How do you work out % yield?

A

Theoretical mass: Mr of reactants
moles = mass/Mr [DON’T RATIO HERE]
ratio out moles for products
Mass = moles x Mr of products
Actual yield (given) / Your theoretical yield x 100
Reasons why it was less: reversible reactants in impurities

12
Q

What is atom economy?

A

mass of desired products / total mass of reactants x 100

13
Q

How do you work out atom economy?

A

No given numbers
Divide the Mr of the desired product / Mr of ALL THE REACTANTS x 100
NO RATIO

14
Q

If there is only one product…

A

The atom economy must be OVER 100%

15
Q

Why is a higher atom economy better?

A
  • less disposable cost
  • less waste
  • cheaper to manufacture
16
Q

What are isotopes?

A

Atoms of the same element with the same number of protons but a different number of neutrons.

17
Q

Chemical and physical properties of isotopes?

A

Chemical: same because the arrangement of electrons are the same.
Physical: Different because the mass will slightly vary.

18
Q

% isotopic abundance?

A

The % of each isotope that naturally occurs o earth
Different in space- different %’s (isotopic signature)
Values in data book and mass spec data is going to be different because the % isotopic abundance is going to be different.

19
Q

Ideal Gas properties and realistic?

A

Particles are constantly in motion
They’re constantly colliding
These collisions don’t produce reactions
Kinetic energy is conserved
No intermolecular forces that divert their path range.
Real gasses DO have intermolecular forces that divert the path of particles.
Some can act like ideal gasses under limited temperature and pressure ranges.

20
Q

Idea; Gas Equation?

A

pv = nRT

21
Q

Conversions for cm3, dm3> m3?

A

cm3 x 10-3 = dm3
dm3 x 10-3 = m3
cm3 x 10-6 = m3

22
Q

Conversions for degrees>kelvin

kPa/Mpa>Pa

A

Degrees + 273 = K
kPa x 10-3 = Pa
mPa x 10-6 Pa

23
Q

To work out Mr for ideal gas equation?

A

n = PV/RT
n (moles) = mass/Mr
Mr = moles / mass

24
Q

How do you work out concentration?

A

conc = moles/ vol

25
Q

standard solutions?

A

solutions where a known volume is used

26
Q

titrations are used for?

A

used to find out a volume of an an acid of a base at a particular concentration.

27
Q

Conversion for dm3?

A

cm x 10-3 = dm3

1l = 1dm3

28
Q

To find it in g/dm-3 instead of mol/dm-3?

A

work out concentration in mol/dm-3 and x Mr

29
Q

if it gives you a neutrilisation reaction to work out the unknown concentration?

A

work out the moles of the other thing using conc and vol
ratio out the moles
work out the conc using the moles and the volume it gave

30
Q

If it gives you a amount of the original soltution and asks you to work out the mass used in the original soltuion?

A

Work out the moles conc x vol
This is for the sample (e.g. 25 cm3 of the original 250 cm3)
Times the moles by the same amount for the sample to go into the original amount e.g. 25 x 10 = 250
Do mass = moles x Mr

31
Q

Mass spectromy can be sued to find?

A

% isotiopic abundance

realtive atomic mass

32
Q

Low-resolution mass soectormy is..?

A
uslly used (1 d.p)
high= 5 d.p
33
Q

Steps of mass spectrometer?

A

1) Vaporization- mas is heated into solid
2) Ionisation- beam of electorns form a high-energy elctron gun>remove electrosn to make atoms into 1+ ions
3) Acceleration= The ions are attratced tp th negatively charged plates>produce an electric field acclerates them twowards the electromagnet
4) Deflection- The elctromagnet produces a magnetic field>deflects them at right-snglers from direction of travel
5) Hit a detector (straight line down)- small electric signal generates current (gives you the % abundance)

34
Q

What infleunces the deflection?

A
  • lighter ions deflecte dmore (away)/heaveir less
    -ions wiht positive charge deflected more
    -operating conditions- stronger magnetic field deflect them more
    temperature no difference
35
Q

working out relatvie siotopic aabundance?

A

m/z value x % abundance divided by 100

36
Q

working out relative atomic mass/intensity?

A

m/z value x relative atomic/intensity divied by sum of the relatve atomic mass/intensity
assume the % abundanc/relative aotmic mass/intensity is 1 unless it tells you

37
Q

if one moelcuel has got a lone pair and the other hasn’t got any lone pairs it might be?

A

dative/co-ordiante bonding by the one that has got a lone pair

38
Q

selenium deviates from the trend in Group 7 as?

A

it should take a huigher meltng point but they are psired electorns in the 4p orbital

Decks in AS Level Class (74):