Consider the reaction below. Upper Z n (s) plus upper C u superscript 2 plus (a q) right arrow upper Z n superscript 2 plus (a q) plus upper C u (s).

Which half reaction correctly describes the oxidation that is taking place?
Z n (s) right arrow upper Z n superscript 2 plus (a q) plus e superscript minus.
Upper Z n (s) right arrow upper Z n superscript 2 plus (a q) plus 2 e superscript minus.
Upper C u superscript 2 plus (a q) plus 2 e superscript minus right arrow upper C u (s).
Upper C u superscript 2 plus (a q) plus e superscript minus right arrow upper C u (s).

Explanation:

Zn(s) + Cu⁺( aq) ⇒ Zn⁺²( aq ) + Cu(s)

In oxidation reaction of an element or ion , the oxidation number is increased . Oxidation no is total charge on the atom or ion

In the following half reaction Zn(s) is oxidised to Zn⁺²

Zn( s ) ⇒ Zn⁺²(aq)  + 2e⁻

In this reaction charge on Zn(s) is zero

After reaction charge on formed Zn⁺² is +2 . Hence there is increase in oxidation number from 0 to + 2 . Hence Zn(s) is oxidised to Zn⁺² ion .  

a is the answer to this question

explanation:

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%