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Solve the following.
The osmotic pressure of 20 g haemoglobin in 500 ml of solution is 0·016 atm at 25°C. Calculate the…
The osmotic pressure of $20\text{ g}$ haemoglobin in $500\text{ ml}$ of solution is $0\cdot016\text{ atm}$ at $25^\circ\text{C}$. Calculate the molecular mass of haemoglobin.
Answer
Answer
Formula used: Osmotic pressure: pi = i*C*R*T with R = 0.0821 L atm K^-1 mol^-1, T = 298 K, V = 0.5 L, pi = 0.016 atm, w2 = 20 g, so M2 = 61164.5 g mol^-1
Formula: $\Pi = \dfrac{w_2 R T}{M_2 V}$, so $M_2 = \dfrac{w_2 R T}{\Pi V}$
Substitution:
$w_2 = 20\text{ g}$, $V = 500\text{ mL} = 0\cdot5\text{ L}$, $T = 25 + 273 = 298\text{ K}$, $\Pi = 0\cdot016\text{ atm}$, $R = 0\cdot0821\text{ L atm K}^{-1}\text{mol}^{-1}$
$M_2 = \dfrac{20\text{ g} \times 0\cdot0821\text{ L atm K}^{-1}\text{mol}^{-1} \times 298\text{ K}}{0\cdot016\text{ atm} \times 0\cdot5\text{ L}} = 6\cdot12\times10^{4}\text{ g mol}^{-1}$
Final answer: 61164.5 g mol^-1