What is the molecular mass of Carbon Dioxide (CO_2)? (Atomic m... | General Science MCQ | Examoogle

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General ScienceChemistry: Atoms and Molecules

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What is the molecular mass of Carbon Dioxide $(CO_2)$ ? (Atomic masses: C=12, O=16)

28 u

44 u

32 u

40 u

Correct Answer

🔬 SC • Science Concept & PrincipleGeneral ScienceChemistry: Atoms and Molecules

Option B

44 u

Quick Summary:

The molecular mass of a compound is the sum of the atomic masses of all atoms present in one molecule. For $CO_{2}$ , this is calculated by adding the mass of one Carbon atom and two Oxygen atoms.

🔬SCScience SolutionConcept & Principle

💡 Explanation

The molecular mass of a compound is the sum of the atomic masses of all atoms present in one molecule. For $CO_{2}$ , this is calculated by adding the mass of one Carbon atom and two Oxygen atoms.

💡 Everyday Analogy (Real-World Intuition)

Think of calculating the molecular mass like calculating the total weight of a sandwich: you sum the weight of the bread slices and the filling separately to get the total.

🔢 Key Formulas

$\text{Molecular Mass} = \sum (\text{Number of atoms} \times \text{Atomic mass})$

$\text{Mass of } CO_{2} = (1 \times 12) + (2 \times 16) = 44\text{ u}$

⚙️ Working Principle

According to the principle of conservation of mass in chemical formulas, the molecular mass is found by multiplying the atomic mass of each element by its subscript in the chemical formula. Here, $CO_{2}$ consists of one atom of Carbon (mass $12\text{ u}$ ) and two atoms of Oxygen (mass $16\text{ u}$ each). The total mass is determined by the sum: $1 \times 12\text{ u} + 2 \times 16\text{ u}$ .

📌 Key Points

▸
Atomic mass of Carbon (C) is $12\text{ u}$ .
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Atomic mass of Oxygen (O) is $16\text{ u}$ .
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Molecular mass is a scalar quantity measured in unified atomic mass units (u).

✅ Advantages

▸
Allows for precise stoichiometric calculations in chemical reactions.

🛠️ Applications / Uses

▸
Calculating molarity of solutions.
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Determining the mass of reactants needed for industrial synthesis.

📄 Additional Information

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The unified atomic mass unit ( $u$ ) is defined as one-twelfth the mass of a carbon-12 atom.
▸
Option A ( $28\text{ u}$ ) is the mass of $CO$ (Carbon Monoxide), Option C ( $32\text{ u}$ ) is the mass of $O_{2}$ (Oxygen gas), and Option D ( $40\text{ u}$ ) corresponds to the atomic mass of Calcium.

📊 Diagram / Illustration

✅

B is correct — The molecular mass of Carbon Dioxide is $12 + (2 \times 16) = 44\text{ u}$ .

Core Concepts Used

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Atomic Mass Molecular Mass Stoichiometry

💡 EXAM TIP

Always memorize the atomic masses of common elements like H(1), C(12), N(14), O(16), Na(23), and Cl(35.5) to speed up calculations in competitive exams.

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