Reactivity Trends ✅ Flashcards
What are group 2 elements in redox reactions
Reducing agents
What is created from a group 2 metal and oxygen, describe oxidation state and numbers
Metal oxides,
oxidation=magnesium, +2
Reduction=oxygen, -2
What is created from a group 2 metal and water, describe oxidation state and numbers
Alkaline hydroxide
Sr= oxidation, +2
Hydrogen= reduction,-2
What is created from a group 2 metal and dilute acids, describe oxidation state and numbers
Salt +hydrogen gas
Magnesium=oxidation, +2
Hydrogen=reduction,-2
What are the trends in reactivity (with water, oxygen, hydroxides and acids) and ionization energy In group 2
What is trend in melting point going down group 2
Reactivity increases down the group with all 4
Ionization energy decreases down the
Group
Melting points decreases
Why does reactivity increase down group 2
Want to be oxidized
Further away the electron is, easier it is to lose
Atomic radius increases, more electron shielding, nuclear attraction, less energy required to overcome it as they are two factors meaning it is easier to lose against one making it harder
What is formed from group 2 compounds and water
Alkaline solutions of metal hydroxide and hydroxide ions
How does the solubility of the hydroxides change going down group 2
Increases, resulting solutions contain more OH- ions and are more alkaline
How are group 2 compounds used in every day life
Neutralize acids
Agriculture (increase soil pH)
Medicine (acid indigestion)!
At room temp and pressure what are the halogens
Diatomic molecules
What structure does halogens that are solid have
Lattices with simple molecular structures
Why are the halogens oxidizing agents
Because it has oxidized another species
What colour are chlorine solution in water and cycohexane
Water: pale green
Cyclohexane: pale green
What colour are bromine solution in water and cycohexane
Water: oranje
Cyclohexane: oranje
What colour are iodine solution in water and cycohexane
Water: brown
Cyclohexane: violet
What order of reactivity is bromine iodine and chlorine in, so what displaces what
Chlorine, bromine, iodine
Chlorine displaces both, bromine only iodine
How does reactivity change going down the group for halogens and why
Decreases
Atomic radius increase, more inner shells do more shielding, less nuclear attraction to capture another electron, reactivity decreases
What is disproportionation
Redox reaction in which same element js both oxidized and reduced
What type of reaction is chlorine with water and why
Disproportionation
Chlorine both oxidized and reduced
What is added to test for halide ions
Aqueous silver ions added to aqueous halide ions to form a precipitate
Describe the carbonate test
Basis for a test for the carbonate ion (CO3,^2-)
In a test tube add dilute nitric acid to solid or solution to be tested
If you see bubbles, unknown compound could be a carbonate
To prove that the gas is CO2, do limewater test (a saturated aq solution of calcium hydroxide)
CO2 reacts to form fine white precipitate or calcium carbonate, turns the solution cloudy
Describe the sulfate test
Most sulfates soluble, barium sulfate isn’t
Aq barium ions are added to a solution of an unknown compound (usually barium chloride and barium nitrate, if doing a halide test after use nitrate)
A white precipitate is formed
How to do the halide test
Add aq silver nitrate, to an aq solution of a halide
Silver chloride is white, silver bromide is cream, silver iodide is yellow
Adding dilute ammonia: chloride is soluable
Adding concentrated ammonia: bromide is soluble, Iodide is Insoluble
What is the correct order to analyze an unknown inorganic compound
Carbonate
Sulfate
Halides
How could you distinguish between NaCl, NaBr and NaI by a simple test (3 marks)
Add AgNO3 (aq) to an aq solution of each. NaCl forms a white precipitate which dissolved in dilute NH3 (aq)
NaBr forms a cream precipitate which concentrated NH3 (aq)
NaI forms a yellow precipitate which is insolvable in concentrated NH3 (aq)
Explain why it is important to carry out the carbonate test before carrying out a sulfate test on an unknown chemical (2 marks)
Dilute nitric acid reacts with carbonate ions and no precipitate of barium carbonate will then form
Explain why, if you are testing a mixture, it is important to use dilute nitric acid, rather than sulfuric or hydrochloric acid, for the carbonate test (2 marks)
If sulfuric acid is used, sulfate ions ate after and will show up the sulfate test with Ba 2+ (aq). If HCl acid is used, chloride ions are added and will show up in the halide test with Ag+ (aq)
State and explain the trend in boiling points of the halogens fluorine to iodine (3 marks)
Boiling point increases due to increase in electrons down the group. This increases the strength of the London Forces and more energy needed to break the intermolecular forces
Explain why group 2 elements are reducing agents (2 marks)
Group 2 metals add electrons to other species
Following reaction is a redox process:
Mg+2HCl=MgCl2+H2
A: identify the changes in oxidation number
B: state which species is being oxidized and which is being reduced (3 marks)
A: Mg changes from 0 to +2, H changes from +1 to 0
B: Mg oxidized, H reduced
Explain why group 2 elements become more reactive down the group (4 marks)
Down group 2, the total energy from 1st and 2nd ionization energies decreases as nuclear attraction on outer electrons decreases as nuclear attraction on the outer electrons decreases because of increases atomic radius and increased shielding. It therefore becomes easier to remove the electrons and the reactivity increases
State and explain the trend in alkalinity of solution formed when group 2 oxides are added to water (3 marks)
Group 2 oxides react with water forming the metal hydroxide. Hydroxide ions in solution cause alkalinity. Down group 2, the solubility of the metal hydroxide increases, increasing the pH and alkalinity
how do you test for ammonia ions
adding hydroxide ions eg NaOH to give NH3+H2O
what forms from group 2 metals and oxygen
metal oxide
what forms from group 2 metals and dilute acids
salt and hydrogen gas
