Module 3 - periodic table and energy Flashcards
How are elements aranged in the periodic table?
proton number
What are the names of groups 1 2 7 and 8?
What is the name of the elements in the middle of the periodic table?
Alkali metals Alkaline earth metals Halogens Noble Gasses
Transition metals
Which elements exist as diatomic molecules?
H2 N2 O2 Halogens: F2 Cl2 Br2 I2
Have No Fear Of Ice Cold Beer
Why do noble gasses have the lowest melting point?
Exist as single atoms
Define metallic bonding
Electrostatic attraction between metal cations and delocalised electrons from the outer shell
Why do melting points increase across the period?
More delocalised electrons
Charges of cations increase
smaller ion = higher charge density:ratio of charge to volume
Define giant covalent structure and their properties
Network of covalently bonded atoms
High melting points
Define allotrope
pure forms of the same element that differ in structure
Group 2 reacts with water to produce …
hydroxides and hydrogen gas
Group 2 reacts with diluted acids to produce …
salts and hydrogen
They burn in oxygen with what characteristic colour?
Brick red
What is the test for Ba 2+ ions?
White pricipitate forms
What are the periodic trends of alkaline earth metals?
Atomic and ionic radius increases down group - more shells
Ionisation energy decreases down group
Reactivity increases down group
Melting points decrease down group
Solubility of oxides and hydroxides increase down group
What is the trend in the halogen group?
Less electronegative down group
Less reactive down group
Melting point/boiling point increase down group
Larger molecules
more electrons
stronger london forces
What are some disadvantages of water treatement with chlorine?
Cl2 harmful and toxic - irritates respiritory system:liquid chlorine burns eyes/skin
Cl2 reacts with organic compounds to form chlorinated hydrocarbons- carcinogenic
What are some alternitives to treating water with chlorine?
ozone
Uv light
What are the tests for all the halides
F- no precipate doesn’t dissolve
Cl- White precipitate dissolves in diluted NH3
Br- crem precipitate dissolves in concentated NH3
I- yellow precipitate insoluble
How to identify halide ions in displacement reactions
F2 yellow gas
Cl2 green gas water-colourless hexane-pale green
Br2 red brown liquid water-yellow/orange hexane-orange/red
I2 black purple solid water-brown hexane-pink/purple
What is the test for carbonates?
Fizzing carbonate dissapears
What is the test for CO2?
lime water turns cloudy
What is the test for sulphate?
white precipitate
What is the test for ammonium?
litmus paper turns from red to blue
What are some common insoluble salts?
silver halides
barium sulfate
most carbonates - except sodium potassium and ammonium carbonates
metal oxides
What are some common soluble salts?
most hydrogen carbonates
most sodium salts
what are the standard conditions for enthalpy change?
100 kPa 298 K
Define standard enthalpy change of reaction
the enthalpy change when the reaction occurs in the molar quantities shown in the chemical equation under standard conditions in their standard states
Define enthalpy change of formation
enthalpy change when 1 mol of a compound is formed from its elements in their standard states under standard conditions
Define enthalpy change of combustion
the enthalpy change when 1 mole of a substance is completely burned in oxygen under standard conditions, all reactions and products being in their standard states
Define enthalpy change of neutralisation
the enthalpy change when 1 mole of water is formed from the neutralisation of hydrogen ions by hydroxide ions under standard conditions
What is the equation for bond enthalpy?
sum of bonds broken - sum of bonds formed
Define bond dissociation enthalpy
bond dissosiation enthalpy per mole of gaseous compound
Define average bond enthalpy
energy needed to break one mole of bonds in the gas phase averaged over many different compounds
This value is ALWAYS positive
Bond forming … energy
Bond breaking … energy
Releases
Requires
Define activation energy
Minimum amound of energy needed to begin breaking reactant bonds and start a chemical reaction
ALWAYS POSITIVE
Which way do arrows point in exo and endothermic reactions?
Exothermic down
Endothermic up
What is the equation for enthalpy change?
q=mcdeltaT
q=enthalpy change m=mass of water c=4.18 deltaT=change in temp
What are some reasons for underestimation of enthalpy change?
Heat absorbed by container and lost to surroundings
Incomplete combustion
Non standard conditions
Define Hess law
The total enthalpy change for a reaction is independant of the route taken (as long as initial and final conditions are the same)
What are some factors that impact the rate of a reaction?
temperature
surface area
catalyst
concentration of reactants
pressure of gasses
What are some methods of measuring rate of reaction
precipitation
change in mass
volume of gas
titration
what is the equation for rate of reaction?
difference in concentration/difference in time
How do you calculate the gradient of a linear graph?
change in Y/change in X
Define catalyst
Increases rate of reaction by lowering activation energy and providing an alternative reaction pathway. Catalysts are not used up during the reaction (unchanged)
What is a homogenous catalyst?
same physical state of reactants, forms intermediates
what is a hetrogenous catalyst?
different physical state to reactant
What is a dynamic equalibrium?
rates of the foreward and reverse reactions are equal
concentrations of reactants and products remain constant
only in closed systems
Define Le Chetalliers principle
When the conditions of a system at equalibrium change, the position of the equalibrium shifts in the direction that opposes the change
How is equalibrium affected by an increase in pressure?
Shifts to the side with fewer moles
What is the equalibrium equation?
aA + bB - cC + dD double arrows
What is equalibrium law?
Kc= (C)c (D)d
(A)a (B)b Brackets concentration
What is Kc dependant on?
Temperature
