Determine the number of moles (of molecules or formula units) in each sample. c. 0.1187 g C₈H₁₈

Verified step by step guidance

1. Identify the molecular formula of the compound, which is \( C_8H_{18} \).
2. Calculate the molar mass of \( C_8H_{18} \) by adding the atomic masses of all the atoms in the formula. Carbon (C) has an atomic mass of approximately 12.01 g/mol, and hydrogen (H) has an atomic mass of approximately 1.01 g/mol.
3. Multiply the number of each type of atom by its atomic mass and sum these values to find the molar mass of \( C_8H_{18} \).
4. Use the formula: \( \text{moles} = \frac{\text{mass (g)}}{\text{molar mass (g/mol)}} \) to calculate the number of moles of \( C_8H_{18} \) in the sample.
5. Substitute the given mass (0.1187 g) and the calculated molar mass into the formula to find the number of moles.

Key Concepts

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). It is calculated by summing the atomic masses of all the atoms in a molecule. For example, to find the molar mass of octane (C8H18), you would multiply the number of carbon atoms by the atomic mass of carbon and the number of hydrogen atoms by the atomic mass of hydrogen, then add these values together.

Moles

A mole is a unit in chemistry that represents 6.022 x 10^23 entities, such as atoms, molecules, or formula units. This number, known as Avogadro's number, allows chemists to count particles by weighing them. The concept of moles is fundamental for converting between mass and the number of particles in a sample, facilitating stoichiometric calculations in chemical reactions.

Conversion from Mass to Moles

To determine the number of moles from a given mass of a substance, you can use the formula: moles = mass (g) / molar mass (g/mol). This calculation allows you to convert the mass of a sample into the number of moles, which is essential for understanding the quantity of reactants or products in chemical reactions. In the case of 0.1187 g of C8H18, you would first calculate its molar mass and then apply this formula.