C3.1 - Introducing Chemical Reactions Flashcards
How are the formula of metals always written and why?
- As an empirical formula.
- Metals exist as giant metallic lattices - Don’t
need to include the numbers because they are
huge and would vary depending on the amount
of metal.
How do elements in Group 0 exist?
- Exist as individual atoms.
- Attracted to each other by weak intermolecular
forces. - Formula are the same as their chemical symbols.
How do the elements of Group 7 exist?
- Diatomic molecules - Two atoms covalently
bonded together. - Attracted to each other by weak intermolecular
forces. - All elements have the subscript 2 in them.
What 3 elements that aren’t in group 7 but also exist as diatomic molecules?
- Hydrogen
- Nitrogen
- Oxygen
How does sulphur and phosphorus exist?
S8 and P4
What does the molecular formula for a simple covalent compound show?
- The symbols for each element is contains.
- The number of atoms of each element in one of
its molecules.
What ions do metals in groups 1,2 and 3 produce?
The same number of positive charges as their non-IUPAC group number.
What charges do transition elements make and what are 2 exceptions?
- Transition metals produce positive ions that
usually have a 2+ charge. - Silver - Ag+
- Iron(III) - Fe3+
What charges do non metals in groups 5,6 and 7 produce?
Negative ions - 8 minus their (non-IUPAC) group number.
What are compound ions?
Compound ions are ions that contain more than one element.
What must be equal in any ionic compound?
The total number of positive and negative charges.
What are the the chemical formula of the 5 compound ions?
Ammonium - NH4+ Hydroxide - OH- Nitrate - NO3- Carbonate - CO32- Sulphate - SO42-
What is the law of conservation of mass?
The principle that states that the total mass stays the same during a chemical reaction, because atoms are not created or destroyed during a chemical reaction.
How can you investigate conservation of mass?
By carrying out a reaction in a closed system (a container in which no substances can enter or leave during the reaction).
Why does the mass sometimes appear to go down during the reaction?
The reaction mixture may be a non-enclosed system and the reaction involves a substance in the gas state.
What do state symbols show and what are the four state symbols?
State symbols show the physical state of each substance in a chemical reaction.
- Solid (s)
- Liquid (l)
- Gas (g)
- Aqueous solution (aq)
What is a half equation?
A half equation is a model for the change that happens to one reactant in a chemical reaction.
How do you write a half equation?
- Write the element -> ion (or vice versa).
- Check to see if the full element is a diatomic and if
it is balance it by adding a 2 behind the ion. - Check the charges on each half of the equation
and figure out how many electrons you need to
take away or add. - Write the amount of electrons you need with the
coefficient being the number you need.
What does an ionic equation show?
An ionic equation shows the ions present in a reaction mixture.
What are spectator ions?
Ions that are in the reaction mixture but do not take part in the reaction.
How is a net ionic equation different from a complete ionic equation?
A net ionic equation leaves out the spectator ions.
Which state do you split into ions in for ionic equations?
Aqueous
How do you write a compound ion in an ionic compound?
In brackets with the subscript being outside the bracket if there is one.
What is Avogadro constant?
The number of entities in one mole of a substance, 6.02 x 1023 (3s.f.).
What is the mole defined as?
The amount of any substance that contains the same number of entities (atoms, ions of molecules) as there are in 12.0g of carbon-12 atoms.
What does one mole of water contain?
- 1 mole of water molecules.
- 3 moles of atoms.
How can you measure a mole of a substance?
The mass of one mole of an element is its relative atomic mass which is also its molar mass (g/mol).
What is the mass of a substance related to?
The mass of a substance is related to its molar mass and amount.
What is the equation to calculate mass?
mass (g) = molar mass (g/mol) x amount (mol)
What does the amount of product formed depend on?
The limiting reactant.
What does stoichiometry describe?
The stoichiometry describes the relative amounts of each substance involved, and is to do with balancing numbers numbers.
How to calculate the stoichiometry of a reaction?
- Calculate the amount (mol) of each measured
substance. - Simplify the ratio of each of the substances.
- Write the numbers in the equation.
