Question

what is the molality of a solution with 35.5 g c₂h₅oh in 450.0 g water? (hint: find the moles of the c₂h₅oh and convert g to kg of water) 0.0789 m 1.71 m 78.9 m 1.75 m

Explanation:

Step1: Calculate moles of \( C_2H_5OH \)

Molar mass of \( C_2H_5OH \) (ethanol): \( C = 12.01, H = 1.008, O = 16.00 \).
Molar mass \( = 2\times12.01 + 6\times1.008 + 16.00 = 46.07 \, \text{g/mol} \).
Moles \( = \frac{\text{mass}}{\text{molar mass}} = \frac{35.5 \, \text{g}}{46.07 \, \text{g/mol}} \approx 0.7706 \, \text{mol} \).

Step2: Convert water mass to kg

Mass of water \( = 450.0 \, \text{g} = 0.4500 \, \text{kg} \) (since \( 1 \, \text{kg} = 1000 \, \text{g} \)).

Step3: Calculate molality

Molality (\( m \)) formula: \( m = \frac{\text{moles of solute}}{\text{kg of solvent}} \).
\( m = \frac{0.7706 \, \text{mol}}{0.4500 \, \text{kg}} \approx 1.71 \, \text{m} \).

Answer:

1.71 m