Adding 4.00g of Zn metal to 90.0mL of 1.00 M HCl in a coffee-cup calorimeter lea

Question

Adding 4.00g of Zn metal to 90.0mL of 1.00M HCl in a coffee-cup calorimeter leads to a temperature increase of 10.2ºC.    Write a balanced net-ionic equation for the reaction of Zn and HCl.

Which one is right ?

Zn(s) + 2 H+ (aq) + 2Cl-(aq) à Zn2+(aq) 2Cl-(aq) + H2 (g)

Zn(s) + 2 HCl(aq)à ZnCl2(aq) + H2 (g)

Zn(s) + 2 H+ (aq) à Zn2+(aq) + H2 (g)  

2H+  à H2

Zn(s) + 2 H+ (aq) + 2Cl-(aq) à Zn2+(aq) 2Cl-(aq) + H2 (g)

Zn(s) + 2 HCl(aq)à ZnCl2(aq) + H2 (g)

Zn(s) + 2 H+ (aq) à Zn2+(aq) + H2 (g)  

2H+  à H2

Explanation / Answer

The balanced molecular equation is

Zn(s) +2 HCl(aq)----->ZnCl2(aq)+H2(g)

Total molecular equation is

Zn(s)+2H+(aq)+2Cl-(aq) ----> Zn2+(aq)+2Cl-(aq)+H2(g)

Spectator ion is Cl-

Cancelling the spectator ion we get net ionic equation.

Zn(s)+2H+(aq)----> Zn2+(aq)+H2(g)

Therefore third option is correct

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