Two elements, V and W, are in adjacent groups in the Periodic Table.

Question 6 [Inorganic chemistry> group7, group 2]

Two elements, V and W, are in adjacent groups in the Periodic Table.

Reference: Past Exam Paper – 9701 March 2016 Paper 42 Q6

Solution:

(a)

Explanations:

-          V’s oxide and W’s oxide is an acidic gas => from right hand side of the periodic table.

-          V forms an anion in the form of VO_m^-  single negative charge on anion is only observed in Group15 and Group 17. Hence Nitrogen and Chlorine are acceptable answers.

-          X are common oxides that you need to pen down from memory. Nitrogen is undoubtedly the easier option.

-          For m take common oxidation states to calculate. For example, N is commonly +5, doing the math to get overall charge as -1 gives m to be 3 [ 1(+5)+m(-2)= -1]

-          W forms anion with net charge +2 => that element iss from Group 14 or Group 16.

-          Anion forms precipitate with Ba²⁺, from memory we know that Barium Sulphate is insoluble/ ppt. Therefore W must be Sulphur.

-          Y can be either of the very common sulphur di and trioxide gas.

-          Anion can be SO₄^2- or SO₃^2- thus, n can be 4 or 3

(b) (white precipitate is BaSO4) descending the group ∆Hsol becomes more endothermic / positive;

 any two from:

∆Hlatt decreases /becomes more endothermic / becomes less exothermic

 ∆Hhyd decreases / becomes more endothermic / becomes less exothermic

∆Hhyd decreases more than ∆Hlatt

Solutions provided by Kashish Varshney, India