Amount of substance Flashcards
What is the value of Avogadro’s constant
6.02 X 10^23 mole^-1
What is Avogadro’s constant
It is the number of particles of a substance in one mole of that substance
What is the symbol of Avogadro’s constant
NA
What is the amount of a substance
The number of moles we have of a substance is called the amount of a substance
Symbol of amount of a substance
n
What is the unit of amount of substance
Mole
What is the symbol of mole
Mol
what do scientists call the mass of one mole
The molar mass
What is the symbol and unit of Molar mass
Mr
G mol^-1
How to calculate molar mass
The molar mass has the same value as the relative atomic mass but the units are g/mol
For a molecule we use the relative molecular mass with the units g/mol
For a giant structure we use the value of the relative formula mass with the units g/mol
What is the amount of substance equation
Mass (g)
Amount of substance (mol) =——————————————————————-
Molar mass (g / mol)
How can we calculate the number of particles
The number of particles = Amount of substance (mol) X The Avogadro’s constant
What is used as a measure of volume in science
The unit decimetre cubed is used ( or known as cubic decimetre {dm^3})
or
Centimetre cubed {cm^3})
How can we convert between dm^3 to cm^3
Cm^3 to dm^3
Dm^3 to cm^3 = X 1000
cm^3 to dm^3 = / 1000
How can we calculate concentration
Amount of substance (mol)
Concentration (mol/dm^3) = ——————————————-
Volume (dm^3)
What is the volume of one mole of a gas at room temperature and pressure
It has a volume of approximately 24dm^3 at room temperature and pressure
What is the value of room temperature
It is considered to be around 20C
what is the value of room pressure
101,000 Pa
What is the ideal gas equation
pV = nRT
What does each symbol stand for in the ideal gas equation
p= pressure (Pa)
V= Volume (m^3)
n= amount of substance (mol)
R= Ideal gas constant
T = temperature (K)
How can you calculate from Kilopascal to pascals
X1000
Why is pressure changed from kilopascal to pascals
One pascal is actually very low pressure therefore gas pressure is usually originally in Kilopascals (KPa).
Therefore, KPa should be converted to pascals (Pa)
Why is m^3 not given in other volumes of either dm^3 or cm^3
One m^3 is a very large volume. Therefore, gas volumes are originally to dm^3 or cm^3
Therefore, the gas volume should be converted to m^3
How to convert from dm^3 to m^3
/ 1000
How to convert from cm^3 to m^3
/ 1,000,000
How to convert from C to K
And from K to C
273 is added to the temperature
273 is subtracted from the temperature
What is the value of the ideal gas constant
8.314 J mol^-1 K^-1
What assumption are made in the ideal gas equation
We assume that the gas molecules are tiny compared to the spaces between them
We assume that there are no forces acting between the gas molecules
We assume that the gas molecules move randomly
We assume that when the gas molecules collide, the collisions are elastic
How can we find the volume of a liquid chemical to determine the molar mass using the ideal gas equation
First we take a gas syringe with a small cap at the end and we use the balance to find the mass of an empty syringe and cap.
Now we remove the cap and draw a small volume of our chemical into the syringe.
We now replace the cap to seal the chemical into the syringe.Next we reweigh the gas syringe containing the chemical plus the cap
Then we calculate the mass of a chemical in the syringe. (Initial mass of empty syringe and cap from the mass of the syringe containing the chemical and cap)
Now we boil the liquid so it turns into a gas. Therefore, the syringe is placed in a beaker of boiling water.Once it has boiled we read the volume of the gas from the scale of the gas syringe. We then use the volume to work out the molar mass of the chemical (only works for chemical with a boiling point less than 100c as that is the b.p for water. Oil can be used for chemical with a higher b.p)
Define the empirical formula
It shows the simplest whole number ratio of the atoms of each element in a compound
How can the empirical formula be calculated
Using the molecular formula and dividing all the numbers by the smallest number
How can we determine the molecular formula from the empirical formula
We first need to calculate the relative molecular mass of the empirical formula and then multiply it so it becomes the empirical formula mass of the compound.
