Q22.24P - Chemistry: Molecular Nature Of Matter And Change

Question

Which group of elements gives each of the following alloys: (a) brass; (b) stainless steel; (c) bronze; (d) sterling silver?

$\begin{array}{l}\mathbf{\text{1.Cu,Ag}}\\ \mathbf{\text{2.Cu,Sn,Zn}}\\ \mathbf{\text{3.Ag,Au}}\\ \mathbf{\text{4.Fe,Cr,Ni}}\\ \mathbf{\text{5.Fe,V}}\\ \mathbf{\text{6.Cu,Zn}}\end{array}$

Step-by-Step Solution

Answer

1. The brass: $\text{Cu},\text{Zn}$.
2. The Stainless steel is made up of the following elements: $\text{Fe},\text{Cr},\text{Ni}$.
3. The Bronze is made up of the elements Cu, Sn, and Zn.
4. $\text{Cu},\mathrm{Ag}$ is used to make sterling silver.

Step 1: Alloy

As a compound or a solution, an alloy is a metallic material made up of two or more elements. The constituents of alloys are usually metals but some alloys consist of even non-metals like carbon.

Step 2: Subpart (a)

Brass is a metal alloy composed mostly of copper $\text{(Cu)}$ and zinc $\text{(Zn)}$ in a proportion of $\text{50-80\%}$.

The alloy becomes stronger and more ductile as the $\text{Zn}$ concentration increases. It's utilised for plating and decorative purposes.

Therefore, the brass is the mixture of $\text{Cu},\text{Zn}$.

Step 2: Subpart (b)

Stainless steel is an iron-based alloy with $\text{73-79\%}$ iron (Fe),$\text{14-19\%}$  chromium (Cr), and $\text{7-9\%}$ nickel .

The inclusion of Cr makes the alloy heat resistant and prevents iron from rusting when a passive layer forms on the surface. It is used to make cutlery and instruments.

Hence, the Stainless steel is made up of the following elements: $\text{Fe},\text{Cr},\text{Ni}$.

Step 4: Subpart (c)

Bronze is a copper-based alloy made up of $70-95\mathrm{\%}$$\left(\mathrm{Cu}\right),1-25\mathrm{\%}$ zinc, and $1-18\mathrm{\%}$ tin Bronze is a ductile metal with a good thermal conductivity and corrosion resistance. Bronze is widely utilised in the creation of statues and casts. 

Hence, the Bronze is made up of the elements Cu, Sn, and Zn.

Step 5: Subpart (d)

Sterling silver is a silver-based alloy made up of $\text{92.5 \%}$ silver (Ag) and $\text{7.5 \%}$ copper (Cu).

The alloy is more resistant to wear and tear than pure silver. Jewelry and dinnerware are regularly made from this alloy.

Therefore, Cu, Ag metals form the sterling silver.