Amount of Substance Flashcards
Define Relative Atomic Mass
The mean mass of an atom of an element,divided by 1/12 of the mean mass of an atom of the carbon-12 isotope
Define Relative Molecular Mass
The mean mass of a molecule of a compound,divided by 1/12 of the mean mass of an atom of the carbon-12 isotope
What is Avogadro’s constant?
6.022 x 10^23
What does Avogadro’s constant allow you to find?
The number of particles present in a sample of a substance with known mass
Number of particles=nL
n=moles L=Avogadro constant
What does the number in Avogadro’s constant allow you to find?
The number of particles present in a sample of a substance with known mass
Number of particles = nL
(n=moles)(L=Avogadro’s constant)
How do you calculate moles?
Mass/Mr
Concentration x volume/1000
What trends do gases and volatile liquids follow when under standard conditions?
Pressure is proportional to temperature
Volume is proportional to temperature
Pressure and volume is inversely proportional
What is the ideal gas equation?
pV=nRT=mRT/Mr
What are the standard units for the ideal question?
p=pressure in pascals
V=volume measured in m³
T=Temperature in Kelvin
n=moles
m=mass in grams
What is the ideal gas constant? What is it equal to?
R
It is equal to 8.31JK-¹mol-¹
What is the empirical formula?
The simplest whole number ratio of atoms of each element in a compound
How is empirical formula found?
Using molar ratios of each element
What is molecular formula?
The true number of each atom in the molecule
How can molecular formula be determined?
Using the Mr of the empirical formula and the true Mr of the molecule.
This gives a multiplier value which can be used to scale up the empirical formula
What must chemical equations be before they are used in calculations?
Balanced
Why must equations be balanced before being used in calculations?
The reacting ratios must be correct
How do you calculate percentage yield?
%yield=Experimental yield/Theoretical mass x 100
How do you calculate atom economy?
%atom economy=Mr or desired product/Mr of reactants x 100
In industrial processes, why is it desirable to have a high atom economy for a reaction?
There is little or no waste product, only the desired product. The process is more economically viable for industrial scale manufacture
Why is a high atom economy beneficial for the environment?
It uses less natural resources and therefore uses less energy
What is Boyle’s Law?
At constant temperature then the product of pressure and volume is constant
P x V = constant
What is Charle’s Law?
At constant pressure then volume is proportional to the temperature
VαT
V/T = Constant
What is Gay-Lussac’s Law?
At constant volume, pressure is proportional to the temperature
PαT
P/T = Constant
What is the yield of a reaction?
The mass of product obtained
What is the theoretical yield?
The maximum theoretical mass of product in a reaction (calculated using the idea of conservation of mass)
What is the actual yield?
The mass of product you get when you actually do the reaction
What is the percentage yield?
The ratio of actual mass of products obtained compared with maximum theoretical mass
What is a titration used to measure?
An unknown concentration of solution by reacting it to a known concentration of another solution
