Comparing Masses: Hydrogen vs. Oxygen Molecules

When comparing the masses of 2 grams of hydrogen and 6.023 × 1021 oxygen molecules, it is important to understand the fundamental concepts of molar mass and Avogadro's number. This article will explore the steps to determine which substance has the greater mass and why.

Understanding the Problem

Firstly, let's clarify the problem statement. The question asks us to compare the mass of 2 grams of hydrogen with the mass of 6.023 × 1021 oxygen molecules. The comparison is based on the atomic and molecular masses, as well as Avogadro's number, which helps us convert the number of molecules to moles.

Steps to Calculate the Mass

Step 1: Mass of 2 grams of Hydrogen

The mass of hydrogen is given as 2 grams. This value remains constant and does not change in the calculation process.

Step 2: Calculate the Mass of 6.023 × 1021 Oxygen Molecules

In this step, we need to convert the number of oxygen molecules to the mass in grams.

Atomic Mass of Oxygen: The atomic mass of oxygen is approximately 16 grams per mole (g/mol). Molar Mass of Oxygen: Since oxygen is diatomic (O2), its molar mass is 32 grams per mole (g/mol) because 16 g/mol for each oxygen atom. Number of Moles in 6.023 × 1021 Molecules: Using Avogadro's number (approximately 6.022 × 1023 molecules/mol), we can find the number of moles.

Calculation:

[text{Number of moles} frac{6.023 times 10^{21} text{ molecules}}{6.022 times 10^{23} text{ molecules/mol}} approx 0.0100 text{ mol}]

Step 3: Calculate the Mass of Oxygen

The mass of oxygen can now be calculated using the molar mass.

Calculation:

[text{Mass} text{Number of moles} times text{Molar mass} 0.0100 text{ mol} times 32 text{ g/mol} 0.32 text{ g}]

Comparison of Masses

Mass of 2 grams of Hydrogen:

2 grams

Mass of 6.023 × 1021 Oxygen Molecules:

0.32 grams

Conclusion: 2 grams of hydrogen has a greater mass than 0.32 grams (6.023 × 1021) oxygen molecules. This is because 2 grams of hydrogen is significantly more than the mass of the specified number of oxygen molecules. The reason lies in the molar mass of hydrogen (about 2 g/mol) and oxygen (32 g/mol).

Key Takeaways

Hydrogen: Molar mass is approximately 2 g/mol. Oxygen (O2): Molar mass is 32 g/mol. Avogadro's Number: Approximately 6.022 × 1023 molecules/mol.

Understanding these concepts is crucial for accurately comparing the masses of different substances in chemistry.