Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

Chemistry Formulae
Relative atomic mass

𝑟
...
a
...
of 78
...
92 respectively
...
a
...
90, calculate the relative
isotopic abundances of 79Br and 81Br
...
02×1023 (particles: atoms/molecules/ions/electrons)
1 mole contains same number of particles as in 12g 12C (6
...
𝑜𝑓 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑠𝑢𝑏𝑠𝑡𝑎𝑛𝑐𝑒 =

𝑛=

𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑚𝑜𝑙𝑒𝑠(𝑛) =

𝑛𝑜
...
4 𝑑𝑚3 𝑎𝑡 𝑠
...
0 𝑑𝑚3 𝑎𝑡 𝑟
...
77% C, 13
...
42% N
...

C
H
N

mass

No
...
0% carbon, 6
...
3% oxygen with a
molecular mass of 60
...
What is the molecular formula of the unknown compound?

Answer: C2H4O2
_____________________________________________________________________________________________
Determining the molecular formula from combustion data
𝑦
𝑦
𝐶 𝑋 𝐻 𝑌 (𝑔) + (𝑥 + ) 𝑂2 → 𝑥𝐶𝑂2 (𝑔) + 𝐻2 𝑂(𝑙)
4
2
_____________________________________________________________________________________________
Oxidation Numbers
...
8 grams of C 6H6O3 produces a 39
...
428

Theoretical yield
0
...
8 = 17
...
0
17
...
83g
_____________________________________________________________________________________________
Ionization Energy
Definition: Energy required to remove 1 mole of electron from gaseous particles
...

𝑋 + (𝑔) → 𝑋 2+ (𝑔) + 𝑒 −
_____________________________________________________________________________________________
Boyle’s Law
Definition:
Boyle’s law states that volume occupied by gas is inversely proportional to pressure from gas, when mass (or mole)
and temperature are made constant
...
0 dm3 at 100kPa
...
0 𝑑𝑚3 )(100𝑘𝑃𝑎) = (300𝑘𝑃𝑎)𝑉2
𝑉2 = 8
...
)

____________________________________________________________________________________________
Charles Law
Definition:
Charles’ Law states that volume occupied by gas is directly proportional to Kelvin temperature, when mass (or
mole) and pressure are constant
...
0 dm3 at 100°C and was heated to 200°C
...

1 mol of gas at 0°C is 22
...
0 dm3
Formula:
V=kn n = moles of gas V = volume filled by the gas k = constant
Example:
1
...
0 dm3 at constant T and P
...


Example
a) Calculate the mole fraction of
i
...
Helium gas

b) Calculate partial pressure of
i
...
Helium gas

_____________________________________________________________________________________________
Dalton’s Law
Total pressure = sum of partial pressure of all gases
Example:
A container is filled with the gases oxygen, neon and argon with partial pressure 10
...
0kPa and 15
...

Calculate total pressure
...
0 + 30
...
0)𝑘𝑃𝑎
= 55
...
31 ( 𝑔𝑎𝑠 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡)
Example:
Liquid X is either ethanol C2H5OH or methanol CH3OH
...
0800g of liquid X is heated in a syringe to
127°C,the vapour produced a pressure 1
...
0 cm3
...
31
a) Calculate relative molecular mass of X (2m)

b) Calculate Mr of C2H5OH
...
(2m)

8

Chemistry Formulae
Specific Heat Capacity
Definition:
The amount of heat energy required to raise the temperature of 1g of the substance by 1°C or 1K
Heat Capacity
Definition:
The amount of heat energy required to raise the temperature of a substance by 1°C or 1K
Unit:
Jg-1K-1
𝑄 = 𝑚𝑐∆𝑇
𝑚 = 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑡ℎ𝑒 𝑠𝑢𝑏𝑠𝑡𝑎𝑛𝑐𝑒 𝑖𝑛 𝑔𝑟𝑎𝑚
∆𝑇 = 𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑡𝑒𝑚𝑒𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒
_____________________________________________________________________________________________
Standard Enthalpy of Neutralisation
Definition:
Enthalpy change when acid reacts with an alkali to produce 1 moles of water measured at 25°C and 1 atm
...
0 cm3 HCl 1
...
0 cm3 NaOH 1
...

Data obtained:
Initial temperature, HCl (aq)

25
...
0°C

Highest temperature of mixture

31
...
0500 mol ]

b) Moles of NaOH reacted [ 0
...
0500 mol ]

9

Chemistry Formulae
d) Heat released from the mixture in kJ given specific heat capacity of 4
...
856kJ]

e)

Enthalpy of neutralisation [-57
...

Formula:
∆𝐻 𝑓 = [𝑡𝑜𝑡𝑎𝑙 ∆𝐻 𝑓 𝑜𝑓 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑠 × 𝑚𝑜𝑙𝑒] − [𝑡𝑜𝑡𝑎𝑙 ∆𝐻 𝑓 𝑜𝑓 𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡𝑠 × 𝑚𝑜𝑙𝑒]
Example:

Calculate the standard enthalpy change of the reaction [+46
...

Formula:
∆𝐻 𝑟 = [𝑡𝑜𝑡𝑎𝑙 ∆𝐻 𝑐 𝑜𝑓 𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡𝑠 × 𝑚𝑜𝑙𝑒] − [𝑡𝑜𝑡𝑎𝑙 ∆𝐻 𝑐 𝑜𝑓 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑠 × 𝑚𝑜𝑙𝑒]
Example:

10

Chemistry Formulae

Calculate the enthalpy change of combustion of ethanol in kJmol-1 [-1260kJmol-1]

_____________________________________________________________________________________________
Hess Law
Definition:
Enthalpy change of reaction depends only on initial state and final state of chemicals
or
Enthalpy change of reaction does not depend on the numbers of steps for that change

∆𝐻 = ∆𝐻1 + ∆𝐻2 + ∆𝐻3
𝑟𝑜𝑢𝑡𝑒 1 𝐴 → 𝐵 ∆𝐻1
𝐵 → 𝐶 ∆𝐻2
𝐶 → 𝐷 ∆𝐻3
______________
𝐴→ 𝐷

∆𝐻4

______________

Example:

11

Chemistry Formulae

a)

Write equation with state symbol for the standard enthalpy of combustion for

i
...


Carbon solid (1m)

iii
...
(1m)

c) Using Hess Law, calculate the standard enthalpy of formation of cyclohexane liquid (2m)

_____________________________________________________________________________________________
Bond Energy
Definition:
Average energy needed to break 1 mole of covalent between 2 atoms, in gaseous state
...

Example:
𝑁𝑎𝐶𝑙(𝑠) + 𝑎𝑞 → 𝑁𝑎+ (𝑎𝑞) + 𝐶𝑙 − (𝑎𝑞)
∆𝐻° = +6𝑘𝐽𝑚𝑜𝑙 −1
Stage 1:
The ions are separated to form free gaseous ions
...

°
𝑁𝑎 + (𝑔) + 𝑎𝑞 → 𝑁𝑎+ (𝑎𝑞)
∆𝐻2 = −390𝑘𝐽𝑚𝑜𝑙 −1
°
𝐶𝑙 − (𝑔) + 𝑎𝑞 → 𝐶𝑙 − (𝑎𝑞)
∆𝐻3 = −380𝑘𝐽𝑚𝑜𝑙 −1

13

Chemistry Formulae

______________________________________________________________________________

Equilibrium constant
aA + bB
cC + dD
𝐾𝑐 =

[𝐶] 𝑐 [𝐷] 𝑑
[𝐴] 𝑎 [𝐵] 𝑏

Example:
In a 5
...
0 mole of sulfur trioxide gas was allowed to decomposed at 500°C
...


∆𝐻 = +197𝑘𝐽𝑚𝑜𝑙 −1
a)

Write and expression of equilibrium constant, according to concentration

14

Chemistry Formulae
b) Determine the initial mole, equilibrium mole and the concentration for each of the substance
SO3
SO2
O2

Initial mole/mol

Equilibrium mole/mol

Concentration/moldm-3

c)

The calculate the value of equilibrium constant, Kc according to concentration and state its unit if any
[0
...


When SO2(g) and O2(g), at partial pressures of 1
...
500 atm respectively, are allowed to reach
equilibrium at 675K, the total pressure in the container is found to be 1
...

[ KP=2

---