The diagram shows three clean iron nails, each partly coated with a different metal, standing in dilute acid. Bubbling is fastest where the coating metal is...
Question 1 Report
The diagram shows three clean iron nails, each partly coated with a different metal, standing in dilute acid. Bubbling is fastest where the coating metal is more reactive than iron. At which nail is bubbling fastest?
Answer Details
Each nail sits in the same dilute acid, so the only variable is the coating metal. Bubbles of hydrogen come from the metal displacing hydrogen from the acid, and the further above hydrogen the metal is, the faster that happens.
Place the three coatings in the reactivity series: zinc is the highest, tin comes below it but is still above hydrogen, and copper lies below hydrogen. So the nail coated with zinc reacts fastest and bubbles most vigorously.
\[\mathrm{Zn + 2HCl \rightarrow ZnCl_2 + H_2}\]
The tin coated nail bubbles slowly, and the copper coated nail gives no bubbles at all because copper cannot displace hydrogen from a dilute acid. The results cannot be equal, since the whole point of the comparison is that reactivity differs. This is also why tin plating protects steel only while the coating stays unbroken.
Download The App On Google Playstore
Everything you need to excel in your exams
