Group 7 and Redox Flashcards
Properties of F2
Yellow gas
Very reactive
Toxic
Cl2 properties
Green gas
Very reactive
Toxic
Br2 properties and uses
Orange liquid
Very reactive
Toxic
Often used as a solution in water -bromine water Br2(aq)
I2 properties
Grey crystals
Reactive
Toxic
Easily turns into purple vapour on heating
Used in solution as antiseptic
Trend in atomic radius
Atomic radius increases
More shells/more shielding
Bigger atoms
Trend in electronegativity
Electro negativity decreases
Bigger atoms/more shells
More shielding
Weaker attraction between nucleus and 2 electrons in covalent bond
What is electronegativity
The power of an atom to attract the 2 electrons in a covalent bond
Melting and boiling point trend
Increases
Bigger molecules
More VDW forces
Higher mpt/bpt between MOLECULES
Trend in first ionisation energy
Decreases
Atoms get bigger / more shells
More shielding
Therefore weaker attraction from nucleus to electron in outer shell I’m
What is the reaction equation for Cl2 and Br-?
Cl2 + 2 Br- → 2 Cl- + Br2
This reaction shows the conversion of chlorine and bromide ions to chloride ions and bromine.
What color solution forms when bromine is present in aqueous solution?
Yellow solution forms
This indicates the presence of bromine in its aqueous form.
What is the reaction equation for C/2 and I2?
Cl2 + 21- → 2 Cl- + I2
What happens to the solution when Br2 is added to I-?
Brown solution forms
This indicates the formation of iodine in the solution.
What is the reaction equation for Br2 and I-?
Br2 + 2I- → 2 Br- + I2
This reaction results in the formation of bromide ions and iodine.
What color solution does I2 form in aqueous solution?
Brown solution forms
This indicates the presence of iodine in its aqueous form.
What happens to the solution when I2 is present?
Stays brown solution (no reaction)
This indicates that there is no further reaction occurring in the presence of iodine.
What is the state of Br2 in aqueous solution?
Stays yellow solution (no reaction)
This indicates that bromine remains in its aqueous form without reacting further.
What is the trend of oxidising power among halogens?
Cl, > Br2 > I2
This trend indicates that chlorine is the strongest oxidising agent among the three.
What happens when a halogen acts as an oxidising agent?
It gains electrons (taken from the oxidised species)
This process is represented by the equation: X2 + 2e- → 2X.
Fill in the blank: When a halogen gains electrons, the reaction can be represented as _______.
X2 + 2e- → 2X
Why does the ability of halogens to gain electrons decrease down the group?
Atoms are larger & there is more shielding (due to extra electron shell)
This increased distance and shielding makes it harder for halogens to attract additional electrons.
True or False: It becomes easier to gain an electron as you move down the group of halogens.
False
What is the reaction of Cl2 and 2 Br-?
cl2 + 2Br- =2 Cl- + Br2
This reaction indicates the formation of chloride ions and bromine.
What color solution forms in the organic layer when Br2 is produced?
Yellow solution
The yellow solution indicates the presence of bromine in the organic layer.
What is the reaction cl2 + I-
cl2 + 2I-=2 CI- + I2
This reaction shows the formation of iodide ions and iodine.
What color solution forms in the organic layer when I2 is produced?
Purple solution
The purple solution indicates the presence of iodine in the organic layer.
What is the result of the reaction Br2 + I-
Br2+2I- = 2Br-+ I2
This reaction results in the formation of bromide ions and iodine.
What is the chemical reaction for burning magnesium?
2Mg (s) + O2(g) → 2MgO (s)
This represents the combustion of magnesium in the presence of oxygen.
What process occurs when magnesium burns?
Oxidation
Oxidation involves the addition of oxygen to a substance.
What happens to magnesium during its oxidation?
Magnesium is oxidised to magnesium oxide
The resulting compound is magnesium oxide (MgO).
What is an oxidising agent?
An oxidising agent allows oxidation to happen by providing oxygen
In the reaction of burning magnesium, which substance is the oxidising agent?
Oxygen
Oxygen is responsible for oxidising magnesium in the reaction.
What is the chemical reaction for reducing copper oxide?
CuO/s) + H2 (g) → CU/s) + H2 (l)
This reaction shows the transformation of copper oxide to copper through reduction.
What does reduction involve?
Removing oxygen
In the context of this reaction, reduction refers to the process of removing oxygen from copper oxide.
What is reduced in the reduction of copper oxide?
Copper oxide is reduced to copper
This indicates that copper oxide loses oxygen and becomes elemental copper.
What is a reducing agent?
A reducing agent is a substance that donates electrons to another substance, causing the reduction.
Which substance acts as the reducing agent in the reduction of copper oxide?
Hydrogen
In this reaction, hydrogen provides the electrons needed to reduce copper oxide.
What type of reaction is CuSO4 + Mg(s) → MgSO4 (aq) + CU(S)?
Redox reaction
Reduction and oxidation occur in this type of reaction.
What elements are involved in the reaction CuSO4 + Mg(s)?
Copper (Cu), Sulfur (S), Magnesium (Mg), Oxygen (O)
The reaction includes these elements in the compounds.
In the reaction CuS Of + Mg(s), what happens to oxygen?
No oxygen is involved
This distinguishes redox reactions from others that require oxygen.
Fill in the blank: The reaction CuS Of + Mg(s) → MgSO4 (aq) + CU(S) is an example of a _______ reaction.
Displacement reaction
What is the oxidation number of elements?
0
This applies to all elements in their standard state.
What is the oxidation number of H2?
0
H2 is a diatomic molecule where each hydrogen atom has an oxidation state of 0.
What is the oxidation number of Na?
0
Sodium (Na) in its elemental form has an oxidation state of 0.
What is the oxidation number of each element in a simple ion?
The oxidation number of each element is the same as its charge.
What is the overall oxidation number for an uncharged ionic substance?
The overall oxidation number is 0.
What is the oxidation number of Na in NaCl?
+1
What is the oxidation number of Cl in NaCl?
-1
What is the oxidation number of Al in AlBr?
+3
What is the oxidation number of Br in AlBr?
-1
What is the chemical symbol for Hydrogen?
H
In which group of the periodic table is Hydrogen classified?
Group 1
In which group of the periodic table is Aluminium classified?
Group 2
What is the oxidation state of Hydrogen when not joined to a metal?
+1 (unless joined to a metal, -1)
What is the oxidation state of Aluminium?
+3
What is the oxidation state of Oxygen?
-2
What is the oxidation state of Fluorine?
-1
What is the oxidation state of Chlorine?
-1
What is a compound ion?
A group of atoms covalently bonded that have an overall charge
How are compound ions treated in terms of oxidation numbers?
Exactly the same as molecules
What must the overall oxidation number of a compound ion add up to?
The overall charge
What must be balanced in a chemical equation?
All reactants and products must be balanced
This includes atoms, ions, charges, and electrons.
What law states that mass is conserved in a chemical reaction?
Law of conservation of mass
This law implies that the total mass of reactants equals the total mass of products.
Fill in the blank: The law of conservation of mass states that all reactants and products must be _______.
balanced
What types of entities must be balanced in a chemical equation?
- Atoms
- Ions
- Charges
- Electrons
Each of these entities must be accounted for to ensure a balanced equation.
What are the components allowed in half equations?
The substance you start from, what it is oxidised or reduced to, hydrogen ions (H+), water, and electrons.
In half equations, what ion is used unless the substance is alkaline?
H+
In alkaline conditions, what ion is used in half equations?
OH-
What must be included in a half equation to represent oxidation or reduction?
Electrons
Fill in the blank: In half equations, you are only allowed to write the substance you start from and what it is _______.
oxidised or reduced to
True or False: Water can be included in half equations.
True
What is the reducing power trend among halide ions?
Cl < Br < I-
What happens when a halide ion acts as a reducing agent?
It loses electrons.
What is the general reaction for a halide ion acting as a reducing agent?
2 X → X2 + 2 e
What happens to the ease of losing an electron down the group of halide ions?
It becomes easier to lose an electron.
Why does it become easier to lose an electron down the group of halide ions?
Ions are larger & there is more shielding due to extra electron shell.
What is disproportionation in chemistry?
A reaction where an element simultaneously oxidises and reduces.
What is the reaction of chlorine with water?
Cl2 (g) + H2O (l) = HClO (aq) + HCl (aq)
What happens when universal indicator is added to the solution of chlorine and water?
It first turns red due to acidity and then turns colourless as HCIO bleaches the colour.
What occurs when chlorine is bubbled through water in bright sunlight?
2Cl2 + 2H2O → 4H+ + 4Cl- + O2
What happens to the greenish colour of chlorine water when exposed to sunlight?
It fades as Cl reacts and a colourless gas (O2) is produced.
What is the cause of the greenish colour of chlorine solutions?
The presence of Cl.
What is a primary use of chlorine in water treatment?
To kill bacteria.
What are the benefits of using chlorine for water treatment?
The benefits to health outweigh its toxic effects.
Fill in the blank: Disproportionation is a reaction where an element simultaneously _______ and _______.
[oxidises] and [reduces]
True or False: Chlorine water retains its greenish colour in sunlight.
False
What is the reaction of chlorine with cold dilute NaOH solution?
Cl2 (aq) + 2 NaOH (aq) → NaCl (aq) + NaClO (aq) + H2O (l)
The colour of the halogen solution will fade to colourless.
What is the use of the mixture of NaCl and NaClO?
Used as bleach and to disinfect/kills bacteria
This mixture is effective in sanitizing and cleaning.
What is the IUPAC naming convention for compounds containing sulfur and chlorine with oxygen?
Called sulfates and chlorates with relevant oxidation number given in Roman numerals
Remember to add the oxidation number when naming these compounds.
What is the oxidation number for sodium chlorate(I)?
NaClO
This indicates that chlorine has an oxidation state of +1.
What is the oxidation number for sodium chlorate(V)?
NaClO3
This indicates that chlorine has an oxidation state of +5.
What is the oxidation number for potassium sulfate(VI)?
K2SO4
This indicates that sulfur has an oxidation state of +6.
What is the oxidation number for potassium sulfate(IV)?
K2SO3
This indicates that sulfur has an oxidation state of +4.
What are ammonium ions represented by?
NH4*
In which solutions are ammonium ions present?
Dilute ammonia solution and any ammonium salt, such as ammonium chloride.
How can ammonium ions be identified in a solution?
By adding dilute sodium hydroxide solution and gently heating.
What happens to ammonium ions when heated with dilute sodium hydroxide?
They are converted to ammonia gas.
What color change occurs in damp red litmus paper when ammonium ions are present?
Turns blue.
What is the effect of ammonium ions on damp universal indicator paper?
Turns blue.
Action of AgNo3 on the halides
F- = no precipitate
Cl- = white ppt
Br-= cream ppt
I- = yellow ppt
Action of dilute NH3 On the halides
F-= x
Cl-= soluble
Br-= insoluble
I-= insoluble
Action of concentrated NH3 on halides
F-= x
Cl- = soluble
Br-= soluble
I-= insoluble
What ions can be detected when testing for carbonate ions?
Carbonate ions, CO32-
What is added to the test compound to detect carbonate ions?
An acid, such as dilute hydrochloric acid
What indicates the presence of carbonate ions during the test?
Carbon dioxide gas bubbles
What is used to confirm that the gas produced is carbon dioxide?
Limewater
What happens to limewater when carbon dioxide is bubbled through it?
It turns from clear to milky
Fill in the blank: Carbonate ions can be detected whether in a solid compound or in _______.
solution
What is the formula for sulfate ions?
SO42-
Sulfate ions are polyatomic ions commonly found in various chemical compounds.
What solution is used to detect sulfate ions?
Barium chloride solution
Barium chloride reacts with sulfate ions to form a precipitate.
What is the first step in testing for sulfate ions?
The test solution is acidified using a few drops of dilute hydrochloric acid
Acidification helps to eliminate interference from other ions.
What occurs after adding barium chloride solution to the acidified test solution?
A white precipitate of barium sulfate forms if sulfate ions are present
This precipitation reaction is a key indicator of sulfate ions.
Write the chemical equation for the reaction between barium chloride and sodium sulfate.
BaCl2(aq) + Na2SO4(aq) → 2NaCl(aq) + BaSO4(s)
This equation shows the formation of sodium chloride and barium sulfate.
True or False: Barium sulfate is soluble in water.
False
Barium sulfate is an insoluble compound, which is why it precipitates out of solution.
What is the method to test for hydroxide ions in a solution?
Test a 1 cm depth of solution in a test tube with red litmus paper or universal indicator paper.
What color change indicates the presence of hydroxide ions?
Hydroxide will turn damp red litmus paper blue.
Fill in the blank: Hydroxide ions will turn _______ red litmus paper blue.
damp
What is an alternative method suggested for testing a solution?
Think about how you could use a solution of magnesium ions.
