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Solution chemistry deals with understanding the interactions and concentrations of substances dissolved in a solvent. In this example, caffeine is the solute, and chloroform is the solvent. The concentration of this solution is measured in molality, a useful way to express concentration in solution chemistry.

Molality

• Defined as moles of solute per kilogram of solvent.
• Important because it is temperature-independent, unlike molarity.

For our caffeine calculation, the molality is given as 0.0946 molal, indicating a precise concentration.

Key Takeaways

• Molality does not change with temperature, providing consistent data for reactions.
• Understanding molality is crucial for accurate concentration assessments in chemistry problems.

Molar mass is crucial in converting between grams and moles of a substance. It is the mass of one mole of a given substance, often expressed in grams per mole (g/mol).

The molar mass of caffeine was calculated by summing the atomic masses of each element present in its chemical formula \( \mathrm{C}_{8} \mathrm{H}_{10} \mathrm{N}_{4} \mathrm{O}_{2} \). Here’s how the calculation happens:

• Carbon (C): 8 atoms × 12.01 g/mol = 96.08 g/mol
• Hydrogen (H): 10 atoms × 1.01 g/mol = 10.10 g/mol
• Nitrogen (N): 4 atoms × 14.01 g/mol = 56.04 g/mol
• Oxygen (O): 2 atoms × 16.00 g/mol = 32.00 g/mol

Adding these gives a molar mass of 194.22 g/mol for caffeine.

This calculation enables us to relate moles and grams, pivotal for determining the mass of caffeine dissolved in the solution. Understanding how to calculate molar mass empowers students to carry out conversions vital in chemistry.

To determine how many grams of caffeine were present, we must link molality, molar mass, and solution chemistry.

Steps:1. **Conversion of Solvent Mass to Kilograms:**
The mass of chloroform needs to be in kilograms for molality calculations: 45.0 g equals 0.0450 kg.2. **Finding Moles of Caffeine:**
Using the molality formula: \( n = m \times m_{\text{solvent}} \)
Plugging in the values: \( n = 0.0946 \times 0.0450 \) gives \( n = 0.004257 \text{ moles} \)3. **Calculating Mass of Caffeine:**
With molar mass of caffeine as 194.22 g/mol, the total mass is calculated as:
\( 0.004257 \times 194.22 = 0.8265 \text{ grams} \)Rounding this to three significant figures gives a final result of 0.827 grams. Each calculation’s precision ensures the accuracy of your measurements, demonstrating solution chemistry's step-by-step approach to problem solving.