Q. 3.1 - An Introduction to General, Organic, and Biological Chemistry

Question

3.1 Classify each of the following pure substances as an element or a compound:

a. a silicon ($Si$) chip

b. hydrogen peroxide $\left({\mathrm{H}}_2{\mathrm{O}}_2\right)$

c. oxygen gas $\left({\mathrm{O}}_2\right)$

d. rust $\left(F{e}_2{O}_3\right)$

e. methane $\left({\mathrm{CH}}_4\right)$

Step-by-Step Solution

Answer

a. A silicon chip is a element

b. Hydrogen peroxide is a compound 

c. Oxygen gas is a element

d. rust is a compound 

e. Methane is a compound 

Step 1: Given Information (a)

(a)  The pure substance silicon chip as an element or a compound.

Step 2: Explanation (a)

(a) Silicon is a pure substance which may not be separated into further simpler substance by using chemical methods. Silicon ($Si$) is used as chips in various equipments. Chips consist of small crystals of Silicon ($Si$). It's composed of just one kind of material.
Therefore, a silicon ($Si$) chip is an element.

Step 3: Given Information (b)

(b) The pure substance hydrogen peroxide as an element or a compound.

Step 4: Explanation (b)

(b) Hydrogen peroxide (H₂O₂) has a single covalent bond between the two oxygen atoms, which is called the peroxy (O-O) bond. Since the Hydrogen and oxygen atoms are chemically combined to form Hydrogen peroxide, it is a compound. Hydrogen peroxide can be further broken down into simpler substances, proving that it is a compound.  It is  a strong oxidizing agent.

Step 5: Given Information (c)

(c) The pure substance oxygen gas as an element or a compound.

Step 6: Explanation (c)

(c)

Pure Oxygen gas (O₂) is made up of only one type of element: oxygen. The symbol represents this idea. Since it is made up of atoms of only one element (oxygen atoms), it is an element and not a compound.

Therefore, Pure oxygen gas is an element.

 

Step 7: Given Information (d)

(d) The pure substance rust as an element or a compound.

Step 8: Explanation (d)

(d) Rust $\left({\mathrm{Fe}}_2{\mathrm{O}}_3\right)$ is that the common name for iron oxide. Rust is a product of corrosion, which occurs when oxygen combines with metal ($Fe$) in the presence of moisture (H₂O). Since, it is formed by the chemical combination of two or more atoms of different elements, it is a compound. It can be broken down into simpler substances when treated with chemicals. 
Therefore, rust $\left({\mathrm{Fe}}_2{\mathrm{O}}_3\right)$ is a compound. 

Step 9: Given Information (e)

(e) The pure substance methane as an element or a compound.

Step 10: Explanation (e)

(e) 

Methane (CH₄) is a colourless, odourless gas. It is formed by the chemical combination of atoms of carbon and hydrogen(a hydrocarbon), making it a compound. It is the simplest alkane.

Since methane has atoms of different elements (C & H), it is a compound.