Problem 73 - Chemistry and Chemical Reactivity

Question

What mass is represented by 0.0255 mol of each of the following compounds? (a) \(\mathrm{C}_{3} \mathrm{H}_{7} \mathrm{OH}, 2\) -propanol, rubbing alcohol (b) \(\mathrm{C}_{11} \mathrm{H}_{16} \mathrm{O}_{2},\) an antioxidant in foods, also known as BHA (butylated hydroxyanisole) (c) \(\mathrm{C}_{9} \mathrm{H}_{8} \mathrm{O}_{4},\) aspirin (d) \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CO},\) acetone, an important industrial solvent

Step-by-Step Solution

Answer

(a) 1.53 g, (b) 4.60 g, (c) 4.60 g, (d) 1.48 g

Step 1: Calculate Molar Mass of C3H7OH (Isopropanol)

To find the molar mass of isopropanol (C₃H₇OH), sum the atomic masses: Carbon (C) is about 12.01 g/mol, Hydrogen (H) is about 1.01 g/mol, and Oxygen (O) is about 16.00 g/mol. The molar mass, therefore, is: \(3\times12.01 + 7\times1.01 + 16.00 = 60.10\text{ g/mol}\).

Step 2: Calculate Mass of 0.0255 mol C3H7OH

Multiply the number of moles by the molar mass to get the mass: \(0.0255\text{ mol} \times 60.10\text{ g/mol} = 1.53255\text{ g}\).

Step 3: Calculate Molar Mass of C11H16O2 (BHA)

For BHA, the molar mass is calculated as: \(11\times12.01 + 16\times1.01 + 2\times16.00 = 180.24\text{ g/mol}\).

Step 4: Calculate Mass of 0.0255 mol C11H16O2

Multiply the number of moles by the molar mass: \(0.0255\text{ mol} \times 180.24\text{ g/mol} = 4.59712\text{ g}\).

Step 5: Calculate Molar Mass of C9H8O4 (Aspirin)

The molar mass of aspirin is computed as: \(9\times12.01 + 8\times1.01 + 4\times16.00 = 180.17\text{ g/mol}\).

Step 6: Calculate Mass of 0.0255 mol C9H8O4

Find the mass for aspirin: \(0.0255\text{ mol} \times 180.17\text{ g/mol} = 4.59534\text{ g}\).

Step 7: Calculate Molar Mass of (CH3)2CO (Acetone)

The molar mass of acetone is: \(3\times12.01 + 6\times1.01 + 1\times16.00 = 58.08\text{ g/mol}\).

Step 8: Calculate Mass of 0.0255 mol (CH3)2CO

Calculate the mass for acetone: \(0.0255\text{ mol} \times 58.08\text{ g/mol} = 1.48204\text{ g}\).

Key Concepts

Moles to mass conversion

Converting moles to mass is a fundamental skill in chemistry. It allows us to change a given amount of substance in moles to its corresponding mass in grams. To do this, we need to use the data from the periodic table to find the molecular or molar mass of the compound.

The process involves a simple multiplication:

• Find the molar mass of the compound (sum of the atomic masses of all atoms in the molecule).
• Multiply the number of moles by the molar mass to get the mass in grams.

For example, if you have 0.0255 moles of isopropanol ( C_3H_7OH ) , you would determine its molar mass and then multiply by the number of moles to find the mass. This calculation is crucial in laboratory settings where precise measurements are required.

Organic compounds

Organic compounds are primarily composed of carbon atoms, often in combination with hydrogen, oxygen, nitrogen, and other elements.

They form the basis of life and the materials around us; these compounds are found in molecules from fuels, foods, and pharmaceuticals. In our exercise, compounds like isopropanol, BHA, aspirin, and acetone are examples of organic molecules with different structures and functions.

The structure of these compounds often involves:

• Covalent bonding between carbon and other atoms.
• Branches and chains of carbon atoms.
• Functional groups (like hydroxyl, carboxyl) that determine their properties and reactivity.

This versatility makes organic compounds incredibly important in both chemistry and biology.

Chemical formulas

Chemical formulas represent the composition of compounds using element symbols and numerical subscripts. These formulas are essential in stoichiometry and chemical reactions to ensure we understand the ratio of atoms within a molecule.

Let's break down some terms you'll often see:

• Empirical Formula: The simplest whole-number ratio of each element in the compound.
• Molecular Formula: The actual number of atoms of each element in a molecule.
• Structural Formula: Represents the arrangement of atoms in the molecule.

For instance, in the formula C O15437 3H_7OH , each subscript denotes the number of corresponding atoms present. This guides us not only in understanding the compound's structure but also in calculating the needed molar mass for further conversions.