Question

State a balanced equation for the reaction of sodium with water. Include state symbols With reference to electronic arrangements, suggest why the reaction between rubidium and water is more vigorous than that between sodium and water. Describe and explain what you will see if chlorine gas is bubbled through a solution of potassium iodide. fluoride. Explain why the melting points of the elements decrease down group l and increase down group?

Answer 1

5.

a. 2Na(s) + 2H₂O(l) -----------> 2NaOH (aq.)+ H₂(g)

b. Rb belongs to group I like sodium and hence has same number of electrons in the outermost shell. Rb is more reactive with water than sodium because as we go down the group the size of the atom increases there by increasing the reactivity of the metal.

6.

Cl₂ + KI -----------> KCl + I₂

Cl₂ + KF -----------> no rection

Cl₂ is stronger oxidising agent than I and hence able the reduce I^- to I₂^. F₂ is the strongest oxidising agent among the halogens and hence cannot be reduced by Cl₂ .

7.

In the group I the melting point decreases down the group.The size of the atom increases as we go down the group because the atomic radius of the atom increases. The nucleus of the metal ion is farther away from the outermost electron and hence the metallic bond becomes weaker therby decreasing the melting point.

The bonding between the molecules in case of F₂, Cl₂, Br₂ and I₂ is van der Waal forces. In group 17, the melting increases down the group because of the van der Waals forces operating between the molecules increases because of the increase in the size of the molecules.