C3-Chemical reactions Flashcards
What do chemical equations do?
- model chemical reactions
- show rearrangement of atoms in a reaction and relative mounts of substances involved
What do balanced equations show?
ratio of reactants to products where there are an equal number of atoms of each element on either side of the reaction arrow (law of conservation of mass)
What is the law of conservation of mass
Mass cannot be created or destroyed
What do state symbols show?
The physical state (of matter) of substances in a reaction
What do half equations show?
The change to one reactant in a reaction
Electron transferred during reactions to one reactant
What do complete ionic equations show?
The ions present in a reaction mixture
What do net ionic equations show?
Same as complete ionic equations but omit spectator ions (ions that stay the same on both sides
Usually used to model precipitate reactions
What type of equation is this?
Na(+) + Cl(-) + Ag(+) + NO3(-) -> AgCl + Na(+)+ NO3(-)
Complete ionic
What type of equation is this
Cl(-) + Ag(+) -> AgCl
Net ionic equation
What is a mole (mol)?
A unit for an amount of a substance
Equal to the relative formula/atomic mass but in grams
What is Avogadro’s constant?
Number of entities in 1 mol
6.02x10^23
Equation linking molar mass, amount and mass
Mass (g) = molar mass(g/mol) x amount (mol)
What is the limiting reactant
The reactant that is fully used up in the reaction.It determines the amount of product formed.
What is a redox reaction
Reaction in which both oxidation and reduction
What is oxidation
Loss of electrons
What is reduction
Gain of electrons
What group contains diatomic molecules
Group 7
Properties of exothermic reactions
Temperature increase in surroundings
Energy of products is less than the energy of reactants
Energy change is negative
Eg.combustion, neutralisation
Properties of endothermic reactions
Temperate drop in surroundings
Energy of products is more than the energy of reactants
Positive energy change
Eg.Thermal decomposition, electrolysis, photosynthesis
What is activation energy?
Minimum energy needed to start reaction
Can be brought down by catalysts
Can be supplied by sparks, flames, heating, electrical energy
How do you calculate energy change?
Energy in - energy out = energy change
Bond breaking = endothermic (energy in)
Bond making = exothermic (energy out)
energy of reactants - energy of products = energy change
