Section B: Give a very short answer to the question given below.
"Dil. HCl is added to Zn granules.” How will you prove that chemical change has taken place here? Support your response with two arguments.
"Dil. HCl is added to Zn granules.” How will you prove that chemical change has taken place here? Support your response with two arguments.
To demonstrate that a chemical change occurs when dilute hydrochloric acid \(HCl\) is added to zinc \(Zn\) granules, consider the following observations:
i. Gas Evolution:
The reaction between HCl and zinc produces . You can observe the release of gas bubbles during the reaction, which serves as a clear indication of a chemical change. The generation of gas is evidence for a chemical reaction to take place.
ii. Colour Change:
ii. Colour Change:
Zinc appears as a greyish metal, whereas the reaction product, zinc chloride \(ZnCl_{2}\), is a white crystalline solid. If you examine the zinc granules before and after the reaction, you will notice a color change from . This alteration in color signifies the formation of a new substance (zinc chloride), reinforcing the notion that a chemical change has occurred.
\(Zn_{(s)} + 2HCl_{(aq)} \rightarrow\ ZnCl_{2(aq)}+H_2{(g)}\)
In summary, the observation of gas evolution (hydrogen) and the color change from gray to white when dilute \(HCl\), temperature change (exotheremic reaction) and finally formation of new substance introduces the observations of a chemical change. These findings provide evidence for the formation of zinc chloride through a chemical reaction.