C3.1 - Introducing Chemical Reactions
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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.).