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Tahsili Chemistry (Chemical Calculations) Cheat Sheet by

2024 Tahsili Chemistry, Chemical Calculations


Avogadro's number
6.02 x 1023
Molar Mass
the mass of one mol of a substance

Gas Laws

Boyle's Law (Constant Temp)
P1V1 = P2V2
Graph Shape
a decreasing curve
Charle's Law (Constant Pressure)
V1/T1 = V2/T2
Graph Shape
an increasing line
Gay-Lu­ssac's Law (Constant Volume)
P1/T1 = P2/T2
Graph Shape
an increasing line
General Law
P1V1/T1 = P2V2/T2
Ideal Gas Law
PV = nRT (R = 0.082)
Standard Conditions (STP)
temp = 273 K / 0 C and P = 1 atm
Avogadro's Principle
equal volumes of gases have equal number of particles at the same temp and pressure

Chemical Potential Energy and Heat

Chemical Potential Energy
the stored energy in the structure of matter
the energy transf­erred between objects (Joules)
the amount of energy required to raise 1 gram of water by 1 degree C
Heat Content (H)
the amount of stored heat energy per mol under constant pressure
Change in Heat Content / Enthalpy (ΔH)
the energy absorbed or released in a reaction
Enthalpy Formula
ΔH = H (products) - H (react­ants)
H (products) < H (react­ants)
the reaction is exothe­rmic, and will have a negative value
H (products) > H (react­ants)
the reaction is endoth­ermic, and will have a positive value
Hess's law
states that regardless of the multiple stages, the total enthalpy change is the sum of all the changes
Standard heat of formation
The change in heat content when 1 mol of compound is formed from its elements in standard conditions
endoth­ermic = positive = cold reactions
exothermic = negative = warm reactions
the heat of formation in standard conditions = 0

Empirical and Molecular Formulas

Percent compos­ition of A in AB
( Mass of A / Mass of AB ) x 100%
Empirical Formula
The simplest whole number ratio of atoms (Ex: CH)
Molecular Formula
The actual number of atoms in a molecule (Ex: C6H6)
N whole Number
N = molecular formula mass / empirical formula mass
Hydrated Salts
salts with water molecules in it's crystals
when hydrated salts are heated, they lose their water

Calcul­ations In Gases

Limiting Reactant
the substance that is used up completely
Excess Reactant
the substance that is not used up and remains after the reaction
Theore­tical yield
the largest amount of product that can be produced
Actual Yield
the amount produced by the experiment
Percent Yield
= (actual yield / theore­tical yield) x 100

Kinetic Molecular Theory of Gases

a gas is comprised of molecules whose average distance between each other is greater than the size of its particles
The particles of a gas exert no attractive forces on each other or the container
The particles are in constant random motion
The KE of a particle depends on its mass and velocity

Gas Behavior

the movement of particles from areas of high concen­tration to areas of low concen­tration
Graham's Law of Diffusion
Rate1 / Rate2 = √(molar mass 2 / molar mass 1)
the movement of gases through small holes


the force applied perpen­dic­ularly to the surface of an object per unit area
SI unit
Pascal (N/m2)
measures atmosp­heric pressure
measures the pressure of a trapped gas
Dalton's Law of partial pressure
the total pressure of a mixture of gases is equal to the sum of the individual pressures


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