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What’s a row of elements on the periodic table known as
A period
What’s a column of elements in the periodic table known as
A group
What do elements in the same group have in common
Similar properties
What are the 4 main blocks of the periodic table
S, p, d and f block
What’s the first ionisation energy
The energy required to remove one mole of electrons from one mole of atoms of an element in the gaseous state to form one mole of gaseous ions
what happens to the first ionisation energy across a period
It increases
What happens to the first ionisation energy down a group
It decreases
What factors affect the first ionisation energy
Atomic radius, nuclear charge and electron shielding
Why does the first ionisation energy decrease down a group
The atomic radius increases, electron shielding increases and so the attraction between the nucleus and outer electrons decreases
Why does the first ionisation energy increase across a period
Nuclear charge increases whilst atom radius and electron shielding remains constant increasing the attraction between the nucleus and outer electrons
Why is there a rapid decreases in ionisation energy between the last element in one period and the first element in the next period
The increased atomic radius and electron shielding outweighs the increased nuclear charge
Why do successive ionisation energies of an element increase
Because removing an electron from a positive ion is more difficult than a neutral atom, electron shielding decreases and the proton to electron ratio increases
What are examples of giant covalent substances
Graphite, diamond, graphene and silicon (IV) oxide
What’s the shape and bond angle of diamond
Tetrahedral and 109.5
How many covalent bonds does each carbon form in diamond
4
What’s the shape and bond angle of graphite
Hexagonal and 120
How many covalent bonds does each carbon form in graphite and graphene
3
Why can the layers of carbon slide over each other in graphite
Because the intermolecular forces are weak
What are common properties of metallic substances
High melting and boiling point, lack of solubility and good electrical conductivity
Which giant covalent substances conduct electricity
Graphite and graphene
What’s the trend in melting point across period 2 and 3
The melting point increases from group 1-4 but then a sharp decrease in melting point from group 4-5 as the bonding changes from metallic and covalent to simple molecular
What’s the most common reaction of group 2 elements
Redox reactions
What are elements in group 2 known as
Alkali earth metals
What block are group 2 elements in
S-block
What ions do group 2 elements form
2+
What type of agents are group 2 elements
Reducing agents
What happens to the reactivity of group 2 elements down the group
It increases
Why does the reactivity increase down group 2
The atomic radius increases allowing more electron shielding which decreases the nuclear attraction allowing cations to form more easily
What’s the reaction of group 2 metals with oxygen
2X + O2 → 2XO
What’s the reaction of group 2 metals and water
X + 2H2O → M(OH)2 + H2
What’s the reaction of group 2 metals with an acid (use HCl in the example)
X + 2HCl → XCl2 + H2
What solutions do group 2 oxides form when reacting with water
Alkaline solutions
how does the solubility of group 2 metals change down the group
It increases down group 2
How are group 2 compounds used in agriculture
Calcium hydroxide is soluble in water and so is used to neutralise acidic soil
What the use of group 2 compounds in medicine
Magnesium hydroxide is partially soluble in water and forms milk of magnesia which neutralises excess stomach acid
What’s the trend in the boiling point of the halogens
The boiling point increases down the group
How do halogens exist at room temperature
As diatomic molecules
What intermolecular forces form between the halogens
Weak London forces
Out of chlorine bromine and iodine which is the most reactive
Chlorine
What colour solution does chlorine form as a free halogen
Pale green (sometimes mistaken as colourless)
What colour solution does bromine from as a free halogen
Yellow solution
What colour solution does iodine form as a free halogen
Brown (may include black solid as well)
What type of agent are halogens
Oxidising agents
What does chlorine react with to form a disproportionation reaction
Water and cold, dilute aqueous alkali
Why is chlorine reacting with water useful
It cleans the water making it drinkable
What’s produced in the reaction of chlorine and water
Chloride (I) acid (HClO) and Hydrochloric acid (HCl)
What’s produced in the reaction of chlorine and aqueous sodium hydroxide
Sodium chloride, sodium chlorate and water
What’s a risk of using chlorine to treat water
Chlorinated hydrocarbons could be formed
How can halide ions be identified
By dissolving the solution in nitric acid and adding silver nitrate solution dropwise
Why is nitric acid used to identify halide ions
It reacts with carbonate ions to prevent false positive results
What colour is silver chloride precipitate
White
What colour is silver bromide precipitate
Cream
What colour is silver iodide precipitate
Yellow
What is the follow up test for halide ions
Dilute and then concentrated ammonia is added to the silver halide solution
What’s the solubility of silver chloride
It’s soluble in dilute ammonia
What’s the solubility of silver bromide
It’s soluble in concentrated ammonia
What’s the solubility of silver iodide
It’s not soluble in dilute or concentrated ammonia
What the test for carbonate ions
Add an equal amount of dilute hydrochloric acid and sodium carbonate to a test tube and add the sodium carbonate solution along with a delivery tube that connects to a test tube of limewater
What’s the positive test for a carbonate ion
CO2 forms which forms a white precipitate of calcium carbonate when bubbled through limewater (the limewater turns cloudy)
What’s the test for sulfates
Acidify the sample with dilute hydrochloride acid and then add a few drops of aqueous barium chloride or nitrate
What’s the positive test result for a sulfate
a white precipitate of barium sulphate/barium nitrate
What’s the test for ammonium ions
Reacting the solution with warm aqueous sodium hydroxide forming ammonia gas
What’s the positive result for ammonia
A pungent smelling gas or a gas that turns red litmus paper blue
What’s the total chemical energy inside a substance known as
Enthalpy
What’s an exothermic reaction
A reaction where the products have less energy than the reactants
What happens to the temperature of the environment and the energy of the system
The energy of the environment increases and the energy of the system decreases
What’s the enthalpy change of an exothermic reaction
Negative as the enthalpy decreases
What’s an endothermic reaction
A reaction where the products have more energy than the reactants
What happens to the temperature of the environment and energy of the sytem
The temperature of the environment decreases and the energy of the system increases
What’s the enthalpy change of an endothermic reaction
Positive because the enthalpy increases
What’s activation energy
The minimum amount of energy needed for reactant molecules to successfully collide and start a reaction
What’s the enthalpy change of a reaction
The energy difference from reactants to products
What type of retractions are combustion reactions
Exothermic reactions
What are the standard conditions (pressure temperature and state)
100kPa, 298K and each substance in its standard physical state
What’s the standard enthalpy change of formation
The enthalpy change when one mole of a compound up formed from its elements under standard conditions
What’s the standard enthalpy change of combustion
The enthalpy change when one mole of a substance is burnt in excess oxygen under standard conditions
What’s the standard enthalpy change of neutralisation
The enthalpy change when one mole of water is formed by reacting an acid and an alkali under standard conditions
What’s the standard enthalpy change of reaction
The enthalpy change when the reactants in the stochiometric equation react to give the products under standard conditions
What’s the enthalpy change of formation for an element in its standard state
Zero
How can a calorimeter be made
Using a polystyrene cup
What’s specific heat capacity
The energy needed to increase the temperature of 1g of a substance by 1 degree
What’s the specific heat capacity of water
4.18 j g-1 k-1
What’s the specific heat capacity equation
Heat energy = mass x specific heat capacity x change in temperature
What’s bond enthalpy
The amount of energy required top break one mole of a specific covalent bond in the gas phase
Why are average bond enthalpies used
Because bond energies are affected by other atoms in the molecule (their environment)
What type of reaction is bond breaking
Endothermic as energy is required to break bonds
What type of reactor is bond formation
Exothermic as energy is released making new bonds
What’s Hess’s law
That the enthalpy change from elements to products (direct route) is equal to the enthalpy change of elements forming reactants and then products (the indirect route)
What’s are the equations for Hess’s law
Reactants to products = elements to products - elements to reactants
Elements to products = elements to reactants + reactants to products
What’s the equation for the enthalpy change of formation
Enthalpy change = products - reactants
What’s the equation for the enthalpy change of combustion
Enthalpy change = reactants - products
What’s collision theory
The theory that for a chemical reaction to take place the particles need to collide with each other in the correct orientation and with enough energy
What’s collision frequency
The number of collisions per unit in time
What’s effect does activation energy have on collision frequency
If more particles have more than the activation energy collision frequency will increase
What’s the effect of increased concentration of a solution on collision frequency
Increasing concentration increases collision frequency
What effect does increasing pressure have on collision frequency (in gaseous solutions)
Increasing pressure reduces the area of space for molecules to move increasing collision frequency
What’s the rate of reaction equation
Rate of reaction = change in amount of reactants or products (mol dm-3) / time (seconds)
How can rate of reaction be calculated in a graph
Using a concentration-time graph
How can you work out the rate of reaction from a concentration-time graph
By drawing a tangent from the points plotted on the graph
What’s a catalyst
A substance that increases the rate of reaction by providing the particles with an alternative mechanism with a lower activation energy
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