Formulae and Relative Masses - Theory Flashcards
To understand the theories for formulae and relative masses
Which seven elements exist as diatomic molecules?
The seven elements that exist as diatomic molecules are hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, and iodine.
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.
What is a chemical symbol?
A chemical symbol is a one or two-letter abbreviation used to represent an element in chemical formulas and equations.
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?
Always an empirical formula
What is a balanced equation?
A balanced chemical equation has the same number of atoms of each element on both sides, in accordance with the Law of Conservation of Mass.
What does a symbol equation use?
A symbol equation uses the formulae of the reactants and products to show what happens in a chemical reaction.
What are products?
Products are the new substances which are formed by the reaction of reactants.
What are reactants?
A reactant is a substance that is present at the start of a chemical reaction.
What are spectator ions?
Spectator ions are ions which appear on both sides of an ionic equation and are eliminated from the final equation.
What can occur to ionic compounds in aqueous solutions?
Ionic compounds can dissociate into their constituent ions, react in precipitation reactions, and conduct electricity.
What are the 3 steps to writing ionic equations?
1) Write the full, balanced symbol equation
2) Replace the ionic compounds in the balanced symbol equation with the component ions
3) Remove any ions that appear on both sides of the 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 difference between relative molecular mass and relative formula mass?
Relative molecular mass is used only for covalent compounds, while relative formula mass applies to all compounds, including ionic compounds.
How it the Ar of an element found?
By calculating the weighted average of the atomic masses of all its naturally occurring isotopes, taking into account their relative abundances. (Using a periodic table)
How is the Mr of a substance calculated?
By summing the relative atomic masses (Ar) of all the atoms in a molecule.
