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Ch.3 - Molecules, Compounds & Chemical Equations
Tro - Chemistry: A Molecular Approach 4th Edition
Tro4th EditionChemistry: A Molecular ApproachISBN: 9780134112831Not the one you use?Change textbook
All textbooksTro 4th EditionCh.3 - Molecules, Compounds & Chemical EquationsProblem 65a,c,d
Chapter 3, Problem 65a,c,d

How many molecules are in each sample? a. 6.5 g H2O c. 22.1 g O2 d. 19.3 g C8H10

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Determine the molar mass of water (H2O) by adding the atomic masses of hydrogen and oxygen: \(2 \times 1.01\, \text{g/mol} + 16.00\, \text{g/mol}\).
Calculate the number of moles of water in the sample using the formula: \(\text{moles} = \frac{\text{mass}}{\text{molar mass}}\).
Use Avogadro's number \(6.022 \times 10^{23}\, \text{molecules/mol}\) to convert moles of water to molecules.
Multiply the number of moles by Avogadro's number to find the total number of molecules.
Ensure all units are consistent and check calculations for accuracy.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). For water (H2O), the molar mass is approximately 18.02 g/mol, calculated by adding the atomic masses of its constituent elements: hydrogen (H) and oxygen (O). Understanding molar mass is essential for converting between grams and moles in chemical calculations.
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Avogadro's Number

Avogadro's number, approximately 6.022 x 10^23, is the number of particles (atoms, molecules, etc.) in one mole of a substance. This constant allows chemists to relate the macroscopic scale of substances (grams) to the microscopic scale (molecules). It is crucial for determining how many molecules are present in a given mass of a substance.
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Mole Concept

The mole concept is a fundamental principle in chemistry that provides a bridge between the atomic and macroscopic worlds. It allows chemists to count entities at the atomic scale by weighing them at the macroscopic scale. By using the mole, one can easily convert between the mass of a substance and the number of molecules it contains, facilitating various chemical calculations.
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