1.3 Chemical calculations (re) Flashcards
This may be our downfall, for such a teacher we were given it’s basically gon be solo yolo, but what is the purpose for teachers?
Bruh
You raise a good point!
he definitely raised a good point guys
Formula for relative atomic mass?
75% Cl-35 and 25% Cl-37
% x atomic number / 100
also add em at the top
(75x35)+(25x37)/100
= 35.5
What’s a mass spectrometer?
(3 things)
- An analytical technique
- Used to identify different isotopes
- And find overall relative atomic mass of an element
Explain step 1: Ionisation in mass spectrometry?
(5 things)
- A sample of an element is vapourised and injected
- Into mass spectrometer
- Where high voltage passed over chamber
- Causes electrons to be removed from atoms (ionised)
- Leaving 1+ charged ions in chamber
Explain step 2: Acceleration in mass spectrometry?
(2 things)
- Positively charged ions are accelerated towards
- Negatively charged detection plate
Explain step 3: Ion drift in mass spectrometry?
(4 things)
- Ions deflected by magnetic field
- Into a curved path
- Radius of their path dependent on
- Charge & mass of ion
Explain step 4: Detection in mass spectrometry?
(4 things)
- When positive ions hit negatively charged detection plate,
- They gain an electron
- Producing flow of charge
- Greater current produced = greater abundance
Explain step 5: Analysis in mass spectrometry?
(4 things)
- Current values used in combination
- With flight times to produce
- Spectra print-out
- With relative abundance of each isotope displayed
In mass spectrum, why do we see a half traced version of the ion?
(5 things)
- During ionisation process, 2+ charged ion may be produced
- Will be affected more by magnetic field
- Producing curved path of a smaller radius
- As a result, mass to charge ratio (m/z) is halved
- Can be seen on spectra as a trace at half the expected m/z value
In mass spectrum:
What m/z?
What relative abundance?
> _>
- Mass to charge ratio
- Relative atomic mass?
icl i haven’t seen where u had to put a number for a certain bar so i reckon u don’t get fucked up by this one
I changed it lol
For mass spectra graph, how u gain mass for the 2 isotopes
Formula for mass of 2 isotopes:
1(relative abundance x m/z)+2(relative abundace x m/z)/ra1 + ra2
May seem a lil hard to remember but gl bro B)
How to gain empirical formula?
48.38% carbon, 8.12% hydrogen, rest is O2 (43.50%)
% = their mass
mass/mr = a number (mols?)
then divide that number with it (the smallest number u’ve gained)
double it if the number is not whole
48.38/12 = 4.03 divided by 2.72
8.12/1.01 = 8.02 divided by 2.72
43.5/16 = 2.72 divided by 2.72
(O has a 2, perhaps i should’ve done that 2 to gain real empirical formula)
2.72 is the smallest number
C = 1.5 x 2 = 3
H = 3 x 2 = 6
O = 1 x 2 = 2
C3H6O2
How to gain molecular formula?
CH has molar mass of 78.1g/mol
molar mass/mr empirical formula
CH = 12 + 1.01 = 13.01
78.1/13.01 = 6.00 = 6
C6H6
Formula for moles?
Mass/molar mass = n
How to gain mass of one molecule?
H2
Mr x number of atoms
then divide it by avogadro’s constant (6.02x10^23)
1.01 x 2 = 2.02 mr
2.02/6.02x10^23 = 3.36x10^-24
How to gain number of molecules in a compound?
1.058 mole of H2O
n x avogadro’s constant
1.058 x (6.02x10^23) = 6.37x10^23
How to gain moles from molar volume + volume?
120cm^3 of hydrogen at RTP (24.5 molar volume)
Volume (v) = number of moles (n) x molar volume (Vm)
(also divide volume into dm^3)
0.12/24.5 = 0.0049 or 4.89 x 10^-3
How to understand mole ratio?
H2O + 2H2O
- Gain moles (so use n = m/M)
- The 2 on the second H2O is very important (lol)
1:2 mole ratio - So then that means mols for second H2O
is double mols of first H2O
:v
What is the ideal gas equation?
and what’s the 3 points to note?
pV = nRT
- Temp must be kelvin (0 degrees = 273K)
- Pressure must be in pascals (1atm = 101325 Pa)
- Volume must be m^3 (convert cm by dividing by 10^6)
Define each symbol from ‘pV = nRT’
P = pressure (Pa)
V = volume (m^3)
n = number of moles (mols)
R = molar gas constant (8.31Jmol^-1 K-1)
T = temperature (K)
What’s the simplified gas equation?
and when to use it?
P1V1/T1 = P2V2/T2
Only when the moles remain constant
What equation if number of moles and volume remain constant?
(simplified gas equation)
P1/T1 = P2/T2
What equation if number of moles and temperature remain constant?
(simplified gas equation)
P1V1 = P2V2
What equation if number of moles and pressure remain constant?
(simplified gas equation)
V1/T1 = V2/T2
