Trends of periodic table, enthalpy change Flashcards
exothermic reactions
when energy (heat) is released from a reaction into the atmosphere (have negative bond energies because the reactant lose energy)
endothermic reactions
when energy is taken from the surroundings and into the reaction (have positive bond energies because energy is gained)
what factors increase the rate of reaction
- presence of suitable catalyst
- increased pressure> means that atoms are closer together
- increased concentration of reactants
- heat> gives energy to reactants so move around faster which means more collisions
what is enthalpy change and what is its symbol
ΔH (kj/mol)
this is the energy required for bonds to be made from the reactants to the products
how is enthalpy change calculated
1) find total energy of bonds between reactants (will be positive as is endothermic)
2) find total energy of product bonds (will be negative as exothermic) also may have to multiply energy if there are multiple of the product (eg 2HCl)
3) sum the energies up for the total
columns in p table are?
group number
rows in p table are called?
periods
how are the periods and groups organised?
The rows were assorted by how many outer shells they have. The groups are assorted and all have the same number of outer electrons as their group number
why does reactivity increase when going down group 1 (metal alkali)
because outer shell travels further from the electron
does reactivity increase or decrease when going down group 7 (halogens)
decrease
how to remember metal reactivity series
Polly Saw Lions Crawling (in) Marks Animal Zoo In Croatia, silver, gold
metals in reactivity series (descending reactivity)
Potassium Sodium Lithium Calcium Magnesium Aluminium Zinc Iron Copper Silver Gold
what is a displacement reaction
a reaction when a more reactive substance replaces a lesser reactive one to form a different compound
Less reactive material is pure when displaced
eg. Zinc + Copper Sulphate –> Copper+ Zinc Sulphate
