Question

1. Which of the following is not an example of compound?
A.ammonia C.Hydrogen peroxide
B.HELIum gas D. Table Sugar
2. Which of the following substance is an element?
A. Air C.Salt
B. Iron D. Sugar

Answer 1

1. Helium gas is not an example of a compound, it is an element because it is made up of only one kind of atom. Its symbol is He.

Hence option (B) HELIUM GAS is correct.

2. Iron (Fe) is an element because it is made up of only one kind of atom.

Hence option (B) IRON is correct.

Explanation for questions 1 and 2:

Element:

An element is made up of only 1 kind of atom.

Examples: Iron (Fe), Platinum (Pt) , Hydrogen (H) , Sodium (Na) , Carbon (C)

Compound:

A compound is made up of two or more elements.

Examples:

Ammonia $\bf (NH_3)$,  Hydrogen peroxide$\bf (H_2O_2)$, Table Sugar $\bf (C_1_2H_2_2O_1_1)$, Table salt $\bf (NaCl)$) , Nitric acid $\bf ( HNO_3)$ , Phosphoric acid$\bf ( H_3PO_4)$ , Sodium carbonate $\bf (Na_2CO_3)$ , Hydrochloric acid $\bf (HCl)$, etc.

Air is a mixture of gases.

1. Hence, options A.ammonia,  C.Hydrogen peroxide D. Table Sugar are incorrect because they all are compounds.

2. Hence, options A. Air, C.Salt D. Sugar are incorrect because salt and sugar are compounds and the air is a mixture.

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Answer 2

Helium gas is not an example of compound. Iron is an element.

Answer to Question 1

• Among the given options, helium gas is not an example of compound. So, the correct choice is Option (B).

• Reason: Helium gas is made of only one type of atom Helium. Therefore, it is a molecule. Compounds are those which are made by combining more than one type of element. Therefore, it is not a compound.

• Hydrogen peroxide (H2O2) is made of two different types of atoms (Hydrogen and Oxygen) and hence it is a compound.

• Similarly, ammonia (NH3) is combination of nitrogen and hydrogen. Table sugar (C12H22O11) is made by combining carbon, hydrogen and oxygen. Therefore, these are compounds.

Answer to Question 2

• Among the given options, Iron is an element. So, the right choice is Option B.

• Reason: Iron is an element because it cannot be further broken down into more simpler substances by physical or chemical methods.

• Whereas air, salt and sugar can be broken down into more simpler substances as they are made by combining two or more elements. Hence, these are compounds and not elements.

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