Stoichiometry Flashcards
What does the subscript number in a molecular formula represent?
The subscript number in a molecular formula represents the number of atoms of that element in the molecule.
Define the term simple molecule.
A simple molecule is a molecule made up of a small number of atoms.
What does a molecular formula show?
A molecular formula shows the type and number of atoms in a molecule.
Define empirical formula
Empirical formula is the simplest whole number ratio of the atoms or ions present in a compound.
What type of formula is used for ionic compounds?
The formula of an ionic compound is always an empirical formula.
State the relationship between empirical and molecular formulae.
The molecular formula is a multiple of the empirical formula.
It indicates the exact numbers of each atom in the compound.
What are spectator ions?
Spectator ions are ions which appear on both sides of an ionic equation and are eliminated from the final equation.
Define Ar.
The relative atomic mass, Ar, as the average mass of the isotopes of an element compared to 1/12th of the mass of an atom of carbon-12.
How is the relative atomic mass of an element determined?
The relative atomic mass of an element is found on the Periodic Table.
Define Mr.
Mr is the symbol for the relative formula mass and it refers to the total mass of the substance, which is the sum of the relative atomic masses of all atoms in a molecule.
How is the relative formula mass of a substance calculated?
To calculate the relative formula mass of a substance, you have to add up the relative atomic masses of all the atoms present in the formula.
What does the term molar mass mean?
Molar mass refers to the mass of one mole of a substance.
What is the Avogadro’s Constant?
Avogadro’s constant = 6.02 x 1023
What is the SI unit for amount of substance?
A mole is the SI unit of amount of substance.
Define RTP
RTP is room temperature and pressure, specifically 20°C and 1 atmosphere.
What is the molar gas volume at RTP
The molar gas volume at RTP is 24 dm3 or 24,000 cm3.
What is the equation for calculating the volume of a gas at RTP?
Volume = Moles x Molar Volume
How do you convert cm3 to dm3?
To convert from cm3 to dm3, you divide by 1000.
State the equation for molar gas volume using moles and volume.
Molar gas volume = volume / moles
How do you calculate moles using volume and molar gas volume?
Moles = volume / molar gas volume
Define limiting reactant.
A limiting reactant is the reactant that is completely consumed in a chemical reaction and limits the amount of product formed.
When is a reactant in excess?
A reactant is in excess when there is still some of that reactant left after a chemical reaction is complete.
Why should a chemical equation be balanced before performing reacting mass calculations?
A chemical equation should be balanced before performing reacting mass calculations to ensure that the correct molar ratios are used in the calculations.
What does the concentration of a solution refer to?
Concentration refers to the amount of solid / solute there is in a specific volume of the liquid / solvent.
What are the two common units for concentration?
g / dm3
mol / dm3
State the equation for concentration using moles and volume.
concentration = moles / volume
How do you calculate the volume of a solution using moles and concentration?
