The chemical properties of the halogen elements and the hydrogen halides

a. Which of these mixtures will result in a chemical reaction?

i. bromine solution and sodium chloride solution

ii. iodine solution and sodium bromide solution

iii. chlorine solution and potassium bromide solution

iv. bromine solution and sodium iodide solution

b. Write a balanced chemical equation for each reaction that occurs in part a.

a.

i. No reaction

ii. No reaction

iii. Reaction

iv. Reaction

b.

iii. `Cl _2(aq) + 2KBr(aq) → Br _2(aq) + 2KCl(aq)`

iv. `Br _2(aq) + 2NaI(aq) → I _2(aq) + 2NaBr(aq)`

a. What type of reaction occurs in `Cl _2(aq) + 2KBr(aq) → Br _2(aq) + 2KCl(aq)` ?

b. Rewrite the equation above as an ionic equation

a. This is a redox reaction which involves a transfer of electrons from one species to another that results in a change in oxidation number. Both must occur together.

b. The equation above as an ionic equation

`Cl_2(aq) + 2Br^−(aq) → Br _2(aq) + 2Cl^−(aq)`

Chlorine is a stronger oxidising agent than bromine. Explain why.

Because Cl atoms have smaller radius and they have a higher tendency to gain electrons.

Halogens react with hydrogen gas forming hydrogen halides.

a. Write the equation for the reaction of bromine with hydrogen. State symbols are not required. 

b. State the trend in thermal stability of the hydrogen halides down Group 17. Explain your answer.

a. The equation for the reaction of bromine with hydrogen

`Br_2 (g) + H_2 (g) -> 2HBr (g)`

b. The trend in thermal stability of the hydrogen halides decreases going down the Group 17. This is due to the fact that the atomic radius of the halogens increases when we go down the Group. Bond length increases and less energy is required to break the bond.

Bromine, Br , is acting as an oxidising agent. Order the halogens below from the weakest to strongest oxidising agent.

Bromine, Br₂ 

Chlorine, Cl₂ 

Iodine, I₂

The order the halogens below from the weakest to strongest oxidising agent is iodine < bromine < chlorine. Because when we go down the Group 17, the ability acting as oxidising agents decreases.

The atomic radius of elements increases as one moves down the group, indicating that the outer shells are farther from the nucleus. As a result, as one moves down the group, the halogens' oxidizing power—or capacity to take an electron—will diminish.

Explain why an iodide ion, I^–, is a better reducing agent than a bromide ion, Br^–.

An iodine ion is larger than a bromide ion, leading to the outermost electrons be more shielded by inner shells and less strongly held.

This question is about the reactions and properties of the elements in Group 17 of the Periodic Table. 

Define the term electronegativity and explain the trend in electronegativity seen down Group 17.

The term electronegativity means the ability of a particular atom, which is covalently bonded to another atom, to attract the bond pair of electrons towards itself. 

Trend in electronegativity decreases seen down Group 17 because os increasing atomic radius which results in more difficult to attract electrons density towards itself.

What happens when iodine is bubbled through aqueous potassium bromide?

A. Iodine is oxidised to iodide ions.

B. Potassium bromide is reduced to bromine.

C. Bromide ions are oxidised to bromine.

D. No reaction occurs.

The answer is D.

In Group 17, bromine is higher up than iodine, as such, bromine will be more reactive. Therefore, the iodine will not displace the bromine.

What happens when chlorine gas is bubbled through aqueous potassium iodide?

A. Iodide ions are oxidised to iodine.

B. Chlorine is oxidised to chlorate(V) ions.

C. Chlorine is oxidised to chloride ions.

D. There is no observable reaction.

The answer is A.

In Group 17, chlorine is higher up than iodine, as such, chlorine will be more reactive. Therefore, the chlorine will displace the iodine. 

B is incorrect because there are no oxygen atoms in this reaction, resulting in no chlorate(V) ions generation

C is incorrect because chlorine displaces the iodine from the potassium

D is incorrect because thers is a displacement reaction

When halogen sodium salts react with concentrated sulfuric acid which of the halide ions, chloride, bromide or iodide, acts as a reducing agent?

A. 1, 2 and 3

B. 1 and 2

C. 2 and 3

D. 1 only

The answer is C

The concentrated sulfuric acid serves both as an acid and an oxidising agent.

Only bromine and iodine are strong enough to be reducing agents to reduce such acid, whereas fluoride and chloride ion won’t reduce this concentrated sulfuric acid.