Question

Calculate the potential of the following cell at 298 K. Sn(S)|Sn2+(0.05M)||H+(0.02M)|H2(g)(1bar)|Pt(S) ; E0Sn²⁺/Sn = -0.14V​

Answer 1

Question :

Find product C in the given reaction

• CH3 - OH + PBr3 → A
• A + Alc.KCN → B
• B +H3O + → C

First Learn some rections :

1) Preparation of Alkyl halide from alcohol

R-OH + HCL/anhydrous ZnCl2 → R - Cl

R-OH + PBr3 → R - Br

R-OH + SOCl2 →R - Cl

And other methods also,

2) SN² reaction

It is second order reaction.

Take peace in one step through transition state

Tends proceed with strong nucleophile.

Inversion of configuration take place.

Example :

CH3 - Cl + KCN → CH3 - CN

3) Hydrolysis of Cynaides

Example :

Benzonitrile + H3O + → Benzoic acid

Note if Hydrolysis is partial product is Different in the above reaction.

Solution :

First part reaction is reaction of alcohol with PBr3 : reaction as follows,

CH3-OH + PBr3 → CH3-Br (A)

Second part of reaction :

Reaction of Alkyl halide with alc.KCN

it follows SN² reaction :

CH3-Br + alc. KCN → CH3-CN (B)

Last part of reaction :

Hydrolysis of Cynaides, reaction as follows

CH3-CN + H3O→ CH3-COOH (C)

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Final product C = Ethanoic acid

Answer 2

Answernswer :

Iron. The blue colour of aqueous copper sulphate solution can be changed to place green by immersing an iron rod in it.

Explanation :

Out of the given options, all except silver can displace copper from its solution. But, we are also asked that the solution should be changed to a colour of pale-green. Hence, the answer is iron beacuse the colour of iron sulphate solution is pale-green.

When an iron rod is immersed in the copper sulphate solution it displaces copper from its solution and forms iron sulphate solution which gives a pale green colour to the resultant solution.

Reaction :

\sf{CuSO_4(aq)+Fe(s)\longrightarrow{}\underset{\textsf{pale green}}{FeSO_4(aq)}+Cu(s)}CuSO4(aq)+Fe(s)⟶pale greenFeSO4(aq)+Cu(s)

_____________

Additional Information :

Displacement reaction :

A type of chemical reaction in which an atom or group of atoms displace another atom or group of atoms of a compound. Displacement reactions are also called single-displacement reactions.

Examples :

\sf{CuCl_2(aq)+Zn(s)\longrightarrow{}ZnCl_2(aq)+Cu(s)}CuCl2(aq)+Zn(s)⟶ZnCl2(aq)+Cu(s)

\sf{CuSO_4(aq)+Zn(s)\longrightarrow{}ZnSO_4(aq)+Cu(s)}CuSO4(aq)+Zn(s)⟶ZnSO4(aq)+Cu(s)

\sf{CuCl_2(aq)+Pb(s)\longrightarrow{}PbCl_2(aq)+Cu(s)}CuCl2(aq)+Pb(s)⟶PbCl2(aq)+Cu(s)